Nut found by bird at the end of the line (8)
I believe the answer is:
railhead
'the end of the line' is the definition.
(I've seen this before)
'nut found by bird' is the wordplay.
'nut' becomes 'head' (nut can mean one's head).
'found by' says to put letters next to each other.
'bird' becomes 'rail' (a wading bird).
'head' after 'rail' is 'RAILHEAD'.
'at' acts as a link.
(Other definitions for railhead that I've seen before include "end of the line - with 26d" , "Terminal of the track" , "You've reached the end of the line here" , "End of the train line" .)