Recruit two players from quartet — drum noise heard (5)
I believe the answer is:
enrol
'recruit' is the definition.
(I know that recruit can be written as enrol)
I cannot understand how the remainder of the clue works.
(Other definitions for enrol that I've seen before include "Join up, sing on" , "Join as member" , "register for classes" , "Enlist" , "Register (as student)" .)