One ahead of pace, incensed (5)
I believe the answer is:
irate
'incensed' is the definition.
(thesaurus)
'one ahead of pace' is the wordplay.
'one' becomes 'i' (Roman numeral).
'ahead of' is a charade indicator (letters next to each other) (I've seen this in other clues).
'pace' becomes 'rate' ('rate' can be a synonym of 'pace').
'i'+'rate'='IRATE'
(Other definitions for irate that I've seen before include "Ticked off" , "A tier (anag)" , "Fuming" , "Full of 22" , "Narked" .)