Yell for one during tennis lesson (4)
I believe the answer is:
isle
'yell for one' is the definition.
(Yell is one of the North Isles in Scotland)
'during tennis lesson' is the wordplay.
'during' says the answer is hidden in the clue.
'ISLE' is hidden in the letters of 'tennis lesson'.
(Other definitions for isle that I've seen before include "Wight or Man, say" , "''There is an ..., a bonny ...'' (anthem of Shannon RFC)" , "Small area of land in water" , "Man, for one" , "you can't walk away from" .)