Bird-tender keeping loose hen in grassy area (8)
I believe the answer is:
swanherd
'bird-tender' is the definition.
(someone who looks after swans)
'loose hen in grassy area' is the wordplay.
'loose' is an anagram indicator (letters are loosened from their original positions).
'in' is an insertion indicator.
'grassy area' becomes 'sward' (I've seen this before).
'hen' is an anagram of 'nhe'.
'nhe' inserted within 'sward' is 'SWANHERD'.
'keeping' is the link.
(Other definitions for swanherd that I've seen before include "Bird keeper" , "Person looking after trumpeter" , "Pen-pusher" .)