Birds in box-files? (8)
I believe the answer is:
sparrows
'birds' is the definition.
(sparrow is a kind of bird)
'box-files?' is the wordplay.
'box' becomes 'spar' (spar can mean to box).
'files?' becomes 'rows' (a file is a row of squares e.g. on a chess board).
'spar'+'rows'='SPARROWS'
'in' acts as a link.
(Other definitions for sparrows that I've seen before include "These birds warp Ross badly" , "Small brown birds" , "Small singing birds" .)