Fool goes round close to pit (5)
I believe the answer is:
abyss
'pit' is the definition.
(thesaurus)
'fool goes round close' is the wordplay.
'fool' becomes 'ass' (ass is a kind of fool).
'goes round' indicates putting letters inside.
'close' becomes 'by' (I've seen this in other clues).
'ass' placed around 'by' is 'ABYSS'.
'to' acts as a link.
(Other definitions for abyss that I've seen before include "Very deep gorge" , "gaping hole" , "crevasse" , "Deep hole, seems bottomless" , "Seemingly bottomless chasm" .)