Flyer lags behind, wings clipped (4)
I believe the answer is:
rail
'flyer' is the definition.
(a wading bird)
'lags behind wings clipped' is the wordplay.
'lags behind' becomes 'rai' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'wings' becomes 'll' (abbreviation for left - as in left-wing - repeated).
'clipped' means to remove the last letter (the word is shortened or clipped).
'll' with its final letter taken off is 'l'.
'rai'+'l'='RAIL'
Can you help me to learn more?
(Other definitions for rail that I've seen before include "Bar; waterbird" , "Fulminate - wading bird" , "Protest strongly (at)" , "Kind of transport" , "Scoff" .)