Idiots gathering beside pits (7)
I believe the answer is:
abysses
'pits' is the definition.
(I have seen 'Bottomless pits ' mean 'abysses' so perhaps 'pits' could also mean 'abysses')
'idiots gathering beside' is the wordplay.
'idiots' becomes 'asses' (I've seen this before).
'gathering' indicates putting letters inside (gather can mean to acquire or bring in).
'beside' becomes 'by'.
'asses' going around 'by' is 'ABYSSES'.
(Other definitions for abysses that I've seen before include "Seemingly bottomless pits" , "deep chasms" .)