Work hard in Test to win prize (6)
I believe the answer is:
trophy
'prize' is the definition.
(I know that prize can be written as trophy)
'work hard in test to win' is the wordplay.
'work' becomes 'op' (common abbreviation for 'opus').
'hard' becomes 'h' (abbreviation used in pencil classifications).
'in' indicates putting letters inside.
'test' becomes 'try' (synonyms).
'to win' is an insertion indicator.
'h' inserted into 'try' is 'trhy'.
'op' going inside 'trhy' is 'TROPHY'.
(Other definitions for trophy that I've seen before include "Scalp, prize" , "Award cup" , "Cup or shield given as a prize" , "Memorial of victory" , "Prize, eg cup" .)