Singer capturing large bird fairly quickly (10)
I believe the answer is:
allegretto
'fairly quickly' is the definition.
(I've seen this before)
'singer capturing large bird' is the wordplay.
'singer' becomes 'alto' (type of singing voice).
'capturing' means one lot of letters goes inside another.
'large' becomes 'L' (eg in clothes sizes).
'bird' becomes 'egret' (egret is a kind of bird).
'l'+'egret'='legret'
'alto' going around 'legret' is 'ALLEGRETTO'.
(Other definitions for allegretto that I've seen before include "quite quickly" , "fairly speedily" , "Moving fairly briskly (music)" , "quite fast" , "with reasonable rapidity" .)