Most meagre home for bird on meadow (7)
I believe the answer is:
leanest
'most meagre' is the definition.
'home for bird on meadow' is the wordplay.
'home for bird' becomes 'nest'.
'on' means one lot of letters go next to another.
'meadow' becomes 'lea' (I've seen this before).
'nest' put after 'lea' is 'LEANEST'.
(Other definitions for leanest that I've seen before include "Most skinny" , "most meagre type" , "Least fatty" , "Most unproductive" , "Most thin" .)