Swindle seen in tennis camp (4)
I believe the answer is:
scam
'swindle' is the definition.
(I know that scam is a type of swindle)
'in tennis camp' is the wordplay.
'in' indicates a hidden word.
'SCAM' is hidden in the letters of 'tennis camp'.
'seen' acts as a link.
(Other definitions for scam that I've seen before include "Fraud, trick (slang)" , "Dodgy business" , "ploy" , "Swindle, fraud (colloq.)" , "fiddle" .)