Not quite have time to cover puzzles, essentially reversing instruction (7)
I believe the answer is:
mitzvah
'instruction' is the definition.
(commandment in Judaism)
'not quite have time to cover puzzles essentially reversing' is the wordplay.
'not quite' means to remove the last letter.
'time' becomes 'tim' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'to cover' is an insertion indicator.
'essentially' indicates the central letters.
'reversing' says the letters should be written backwards.
The middle of 'puzzles' is 'z'.
'have' with its last letter removed is 'hav'.
'hav'+'tim'='havtim'
'havtim' enclosing 'z' is 'havztim'.
'havztim' reversed gives 'MITZVAH'.
(Other definitions for mitzvah that I've seen before include "Jewish good deed" , "A good deed (in Judaism)" , "Bar ... , initiation ceremony of 13-year-old Jewish boy" .)