Gather it's an admission that one is a fool (5)
I believe the answer is:
amass
'gather it's an admission that one is a fool' is the definition.
'amass' can be an answer for 'gather' (amass can mean to collect or gather). I'm unsure of the remainder of the definition.
'gather it's an' is the wordplay.
I cannot really understand how this works, but
'gather' could be 'mass' (I've seen this in another clue) and 'mass' is present in the answer.
'an' could be 'a' and 'a' is found within the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for amass that I've seen before include "Stock up on" , "Gathers" , "Accrue, heap up" , "Accumulate, pile up" , "Be a compiler" .)