Best study hard to take in English (5)
I believe the answer is:
cream
'best' is the definition.
(as in 'the cream of the crop')
'study hard to take in english' is the wordplay.
'study hard' becomes 'cram' (to cram is to study hard or intensely).
'to take in' is an insertion indicator.
'english' becomes 'E' (abbreviation).
'cram' going around 'e' is 'CREAM'.
(Other definitions for cream that I've seen before include "Beat" , "'There are more ways of killing a cat than choking it with ....." , "Butterfat part of milk" , "Elite; colour" , "Best - ointment" .)