What may be played in tents that's naughty and full of spirit (10)
I believe the answer is:
instrument
'what may be played' is the definition.
'in tents that's naughty and full of spirit' is the wordplay.
'that's naughty' indicates anagramming the letters.
'and full of' means one lot of letters goes inside another.
'spirit' becomes 'rum' (I've seen this before**).
'tents' with letters rearranged gives 'stent'.
'stent' enclosing 'rum' is 'strument'.
'in'+'strument'='INSTRUMENT'
(Other definitions for instrument that I've seen before include "Word puzzle" , "legal document" , "power" , "Means of precision work (or music-making)" , "What's needed for 1 [MUSICIAN]" .)