Expert serves cold drink, rotating bottles (4)
I believe the answer is:
aces
'expert serves' is the definition.
'aces' can be an answer for 'serves' (ace is a kind of serve). I'm unsure of the 'expert' bit.
'cold drink rotating bottles' is the wordplay.
'cold' becomes 'C' (eg on taps).
'drink' becomes 'sea' ('the drink' can informally mean the sea).
'rotating' says the letters should be written backwards.
'bottles' is an insertion indicator (to bottle can mean to contain).
'sea' reversed gives 'aes'.
'c' going inside 'aes' is 'ACES'.
Can you help me to learn more?
(Other definitions for aces that I've seen before include "Honours" , "excellent service" , "Tennis serves the receiver can't reach" , "They're high and low on cards" , "Top cards or people" .)