Agent keeping out of the wind, far from alert (6)
I believe the answer is:
sleepy
'far from alert' is the definition.
'agent keeping out of the wind' is the wordplay.
'agent' becomes 'spy' (spy is a kind of agent).
'keeping' means one lot of letters goes inside another.
'out of the wind' becomes 'lee' (I've seen this before).
'spy' going around 'lee' is 'SLEEPY'.
(Other definitions for sleepy that I've seen before include "Dozy" , "Ready for bed" , "(Of place) low in activity" , "Somnolent" , "Is inactive" .)