Swindle in tennis camp (4)
I believe the answer is:
scam
'swindle' is the definition.
(scam is a kind of swindle)
'in tennis camp' is the wordplay.
'in' says the answer is hidden in the clue.
'SCAM' can be found hidden inside 'tennis camp'.
(Other definitions for scam that I've seen before include "Fraudulent action" , "Fraudulent trick or swindle" , "A slangy swindle or fraud" , "Confidence trick, swindle" , "'A con, deception (4)'" .)