Perfect angle on a clue (5)
I believe the answer is:
ideal
'perfect' is the definition.
(similar in meaning)
'angle on a clue' is the wordplay.
'angle' becomes 'l'.
'on' says to put letters next to each other.
'a clue' becomes 'idea' (I've seen this in another clue).
'l' after 'idea' is 'IDEAL'.
(Other definitions for ideal that I've seen before include "Model of excellance" , "Perfect for the purpose" , "Optimal" , "fanciful" , "just the job" .)