Is least put out when you leave port (3,4)
I believe the answer is:
set sail
'leave port' is the definition.
(I've seen this before)
'is least put out' is the wordplay.
'put out' indicates anagramming the letters.
'is'+'least'='isleast'
'isleast' with letters rearranged gives 'SET SAIL'.
'when you' acts as a link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for set sail that I've seen before include "Leave port (by ship)" , "have started journey" , "Begin a voyage" , "Left port" , "left land behind" .)