Regularly affable leader of crew on line, working with birds (8)
I believe the answer is:
falconry
'birds' is the definition.
(I've seen this before)
'regularly affable leader of crew on line working' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'leader of' suggests taking the first letters.
'on' is a charade indicator (letters next to each other).
'line' becomes 'ry' (abbreviation for railway).
'working' becomes 'on' (on can mean working or activated).
The initial letter of 'crew' is 'c'.
The alternate letters of 'affable' are 'fal'.
'ry' put after 'on' is 'onry'.
'fal'+'c'+'onry'='FALCONRY'
'with' is the link.
(Other definitions for falconry that I've seen before include "Sport" , "art of hunting with certain birds of prey" , "Keeping of birds of prey" .)