Fool is on time to give help (6)
I believe the answer is:
assist
'give help' is the definition.
(I've seen this before)
'fool is on time' is the wordplay.
'fool' becomes 'ass' (both can mean a stupid person).
'on' says to put letters next to each other.
'time' becomes 't' (abbreviation).
'ass'+'is'+'t'='ASSIST'
'to' acts as a link.
(Other definitions for assist that I've seen before include "Support" , "provide backing" , "Help to make" , "benefit" , "Provide aid, help out" .)