They can't fly me back to the land of the free (4)
I believe the answer is:
emus
'they can't fly' is the definition.
The definition suggests an adverb but the answer is not.
'me back to the land of the free' is the wordplay.
'back' is a reversal indicator.
'to the land of the free' becomes 'US' (United States of America).
'me' backwards is 'em'.
'em'+'us'='EMUS'
Can you help me to learn more?
(Other definitions for emus that I've seen before include "Large flightless birds of Australia" , "Largest native Australian birds" , "laboratory units" , "Running birds" , "Fast, but not high-fliers" .)