Fellow about ready to fight big girl's blouse, say (7)
I believe the answer is:
garment
'girl's blouse say' is the definition.
(I know that blouse is a type of top)
'fellow about ready to fight' is the wordplay.
'fellow' becomes 'gent' (synonyms).
'about' means one lot of letters goes inside another.
'ready to fight' becomes 'arm' (I can't explain this - if you can you should give a lot more credence to this answer).
'gent' enclosing 'arm' is 'GARMENT'.
'big' acts as a link.
This may not be right. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for garment that I've seen before include "Vestment" , "stole, perhaps" , "Article of dress" , "Perhaps shift" , "Item of clothing" .)