Caught with strange instrument (5,4)
I believe the answer is:
snare drum
'instrument' is the definition.
(snare drum is a kind of instrument)
'caught with strange' is the wordplay.
'caught' becomes 'snared' (snaring is a kind of catching).
'with' is a charade indicator (letters next to each other).
'strange' becomes 'rum' (synonyms).
'snared'+'rum'='SNARE-DRUM'
(Other definitions for snare drum that I've seen before include "item in kitchen?" , "one that gets beaten!" , "one's beaten" , "instrument in kitchen" , "nine [RUFF] could come from this" .)