At no time taken in by blow to belly (6)
I believe the answer is:
paunch
'belly' is the definition.
(synonyms)
'at no time taken in by blow' is the wordplay.
'at no time' becomes 'a' (I can't justify this - if you can you should believe this answer much more).
'taken in by' means one lot of letters goes inside another.
'blow' becomes 'punch' (punch is a kind of blow).
'a' put within 'punch' is 'PAUNCH'.
'to' is the link.
(Other definitions for paunch that I've seen before include "corporation" , "Beer belly" , "Beer-belly" , "Fat belly" , "Protuberant belly" .)