Musical sergeant returning cap for sprinkler (6,3)

'sprinkler' is the definition.

'musical sergeant returning cap' is the wordplay.
'musical sergeant' becomes 'pepper' (reference to Beatles character Sergeant Pepper).
'returning' says the letters should be written in reverse.
'cap' becomes 'top' ('top' can be a synonym of 'cap').
'top' reversed gives 'pot'.
'pepper'+'pot'='PEPPER-POT'

'for' acts as a link.