Put down lines quite rejecting it at first (5)
I believe the answer is:
quell
'put down' is the definition.
(I've seen this in another clue)
'lines quite rejecting it at first' is the wordplay.
'lines' becomes 'll' (l is an abbreviation for line).
'rejecting' indicates named letters should be taken away.
'at first' says to put letters next to each other.
'quite' with 'it' taken out is 'que'.
'll' put after 'que' is 'QUELL'.
(Other definitions for quell that I've seen before include "Extinguish" , "Subdue, suppress" , "Suppress completely" , "Put down" .)