Time off insufficient for study (4)
I believe the answer is:
scan
'for study' is the definition.
(I've seen this before)
'time off insufficient' is the wordplay.
'time' becomes 't' (abbreviation).
'off' indicates named letters should be taken away (some letters taken off).
'insufficient' becomes 'scant' (I've seen this in another clue).
'scant' with 't' removed is 'SCAN'.
(Other definitions for scan that I've seen before include "Examine quickly" , "Traverse with a detector" , "Survey - fit in metrically" , "Survey; screen" , "Scrutinise; glance over" .)