To return in top cover? Blather! (3,3)
I believe the answer is:
hot air
'blather' is the definition.
(I've seen this in another clue)
'to return in top cover?' is the wordplay.
'return' is a reversal indicator.
'in' means one lot of letters goes inside another.
'top cover?' becomes 'hair' (hair is a kind of cover. I am not sure about the 'top' bit.).
'to' back-to-front is 'ot'.
'ot' inserted inside 'hair' is 'HOT-AIR'.
Can you help me to learn more?
(Other definitions for hot air that I've seen before include "nothing worth listening to" , "Bombast or balloon filler" , "Guff" , "Boastful talk or balloon filling" , "Boastful talk or balloon filler" .)