Bird is a bargain by the end (5)
I believe the answer is:
snipe
'bird' is the definition.
(snipe is a kind of bird)
'bargain by the end' is the wordplay.
'bargain' becomes 'snip' (slang term for a good deal).
'by' says to put letters next to each other.
'end' says to take the final letters.
The last letter of 'the' is 'e'.
'snip'+'e'='SNIPE'
'is a' is the link.
(Other definitions for snipe that I've seen before include "Game bird" , "Shoot from place of concealment" , "Criticise" , "Shoot; birds" , "The bird to shoot from cover" .)