Perfect plan pursued by student (5)
I believe the answer is:
'perfect' is the definition.
(similar in meaning)
'plan pursued by student' is the wordplay.
'plan' becomes 'idea' (both can mean an intention).
'pursued by' means one lot of letters go next to another.
'student' becomes 'l' (as in L-plates for learner drivers).
(Other definitions for ideal that I've seen before include "principle to be aimed at" , "unlikely to be bettered?" , "Paradigm" , "A deli (anag.)" , "Cutting/stabbing weapons" .)