Ask compiler, ultimately, for puzzle (5)
I believe the answer is:
poser
'puzzle' is the definition.
(I've seen this before)
'ask compiler ultimately' is the wordplay.
'ask' becomes 'pose' ('pose' can be a synonym of 'ask'**).
'ultimately' says to take the final letters.
The final letter of 'compiler' is 'r'.
'pose'+'r'='POSER'
'for' acts as a link.
(Other definitions for poser that I've seen before include "Difficult problem" , "Tricky question" , "Toughie" , "Question; one trying to impress" , "Tricky clue" .)