Leave port out — tea’s quietly brewing (3,2,3)
I believe the answer is:
put to sea
'leave port' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.
'out tea's quietly brewing' is the wordplay.
'quietly' becomes 'p' (p for piano and quiet).
'brewing' indicates anagramming the letters.
'out'+'teas'+'p'='outteasp'
'outteasp' is an anagram of 'PUT TO SEA'.
Can you help me to learn more?
(Other definitions for put to sea that I've seen before include "Set sail" , "Sail away" , "start on the drink" .)