Remarks about fool catching fish (6)
I believe the answer is:
asides
'remarks' is the definition.
(I have seen 'Incidental remarks' mean 'asides' so perhaps 'remarks' could also mean 'asides')
'fool catching fish' is the wordplay.
'fool' becomes 'ass' (both can mean a stupid person).
'catching' means one lot of letters goes inside another.
'fish' becomes 'ide' (type of fish).
'ass' going around 'ide' is 'ASIDES'.
'about' is the link.
(Other definitions for asides that I've seen before include "Remarks not for overhearing" , "Undertones on stage" , "Players aren't meant to hear these" , "Incidental remarks" , "Words spoken from corner of mouth" .)