Solutions for Act III Scene 1 - Tongue Tied

Each line appears to be missing a letter required for it to make sense - for instance the line "girl scots can sell these" seems to be missing a U in order to make it "girl scouts can sell these". Following this pattern, and noting also that the missing letter occurs only once in each line, several lines can be uniquely fixed, resulting in what seems to be a list of word definitions.

For some of these lines the word described is also unique, for instance "weapon that famed Vietnam" can become "weapon that flamed Vietnam" by adding an L, and this obviously refers to the word napalm. Solving each line in this way, it should soon become apparent that the answer to each line contains the line's missing letter. Furthermore, in every case the missing letter is not pronounced in the defined word - we are dealing here with silent letters, which makes sense since the title, Tongue-Tied, both can mean "silent" and contains silent letters itself.

So each line is treating the silent letter of the word it describes as if it does not exist, and so following this pattern it should be straightforward to derive the rest of the words uniquely:

Line Including Missing Letter Word Described
not shifty? honest
marzipan-flavouring? almond
Mars Bars inside part? nougat
remainder of a wrecked ship? debris
knot together with needles? knit
table-snails? escargot
purge oneself from ones job? resign
bread leftovers? crumbs
religious chants? hymns
legally censure? indict
show or feature? exhibit
courteous and charitable? friendly
founder of homes, etc.? builder
in a broad or clear way? unsubtly
eggs gold contents? yolk
assets replacing arrears? mortgages
animal recognised by its long tooth? narwhal
salve for preservation? embalm
sole power holder? monarch
not rarely? often
weapon that flamed Vietnam? napalm
Sicily, for example? island
coral, for example? cnidarian
sent to hell? damned
short of resources? exhausted
girl scouts can sell these? biscuits
what succeeds one? two

Reading off the first letter of each word, we get the message HANDKERCHIEF BUY MNEMONIC DEBT. Each of these words again contains a silent letter, namely D, U, M, and B. These spell out DUMB, which is another word for "silent", or "tongue-tied".

The answer is: dumb