Instrument used in samba and rumba (4)
I believe the answer is:
drum
'instrument' is the definition.
(drum is a kind of instrument)
'in samba and rumba' is the wordplay.
'in' indicates a hidden word.
'DRUM' is hidden in the letters of 'samba and rumba'.
'used' acts as a link.
(Other definitions for drum that I've seen before include "Introductory beats" , "See 18" , "one will be beaten" , "found in the kitchen?" , "Percussion instrument" .)