Piece by piece going topless (7)
I believe the answer is:
article
'piece' is the definition.
(I've seen this before)
'piece going topless' is the wordplay.
'piece' becomes 'particle' (I have seen 'Tiny piece ' mean 'particle' so perhaps 'piece' could also mean 'particle').
'going topless' means to remove the first letter.
'particle' with its first letter taken away is 'ARTICLE'.
'by' is the link.
(Other definitions for article that I've seen before include "Newspaper essay" , "It could be the" , "Definite or indefinite determiner" , "Division" , "thing required" .)