Guard is at the crease late (13)
I believe the answer is:
nightwatchman
'guard' is the definition.
(nightwatchman is a kind of guard)
'at the crease late' is the wordplay.
'at' means one lot of letters go next to another.
'the crease' becomes 'watchman' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'late' becomes 'night' (I've seen this before).
'watchman' after 'night' is 'NIGHTWATCHMAN'.
'is' acts as a link.
Can you help me to learn more?
(Other definitions for nightwatchman that I've seen before include "Guard of premises not in use" , "Earlier than expected arrival at the batting crease?" , "Someone promoted up the ordinary batting order when a wicket falls close to the end of the day's play" , "Inferior batsman" , "one who may take guard close to stumps?" .)