Spot on about caricatures? No sir! (8)
I believe the answer is:
accurate
'spot on' is the definition.
(I've seen this before)
'about caricatures? no sir' is the wordplay.
'about' is an anagram indicator.
'no' suggests deleting specific letters.
'caricatures' with 'sir' removed is 'cacature'.
'cacature' is an anagram of 'ACCURATE'.
(Other definitions for accurate that I've seen before include "faithful" , "Correct, right" , "Spot-on" , "Correct in all details" , "Totally correct" .)