This compiler finally sets small problem (4)
I believe the answer is:
mess
'problem' is the definition.
(thesaurus)
'this compiler finally sets small' is the wordplay.
'this compiler' becomes 'me' (the person who is writing these clues).
'finally' says to take the final letters.
'small' becomes 's' (abbreviation - e.g. clothes size).
The final letter of 'sets' is 's'.
'me'+'s'+'s'='MESS'
(Other definitions for mess that I've seen before include "Canteen - chaos" , "sloppy > food" , "Eating place" , "State of disorder" , "State of confusion or untidiness" .)