Exhausted learner coming in to land very well (3,5)
I believe the answer is:
all right
'very well' is the definition.
(synonyms)
'exhausted learner coming in to land' is the wordplay.
'exhausted' suggests removing the centre (the word is emptied out or exhausted).
'coming in to' means one lot of letters goes inside another.
'land' becomes 'alight' (alighting is a kind of landing).
'learner' with its centre taken out is 'lr'.
'lr' going within 'alight' is 'ALL-RIGHT'.
(Other definitions for all right that I've seen before include "Very well, everything's ok" , "Okay" , "Safe - adequate" , "Nothing left" , "Very well, I agree" .)