Not completely prepared for study (4)
I believe the answer is:
read
'study' is the definition.
('read' can be a synonym of 'study')
'not completely prepared' is the wordplay.
'not completely' means to remove the last letter.
'prepared' becomes 'ready' ('ready' can be similar in meaning to 'prepared').
'ready' with its final letter taken away is 'READ'.
'for' is the link.
(Other definitions for read that I've seen before include "Lecture" , "examined" , "Speak" , "Interpreted, for example" , "Undertake a course of study" .)