Play for the singer (4)
I believe the answer is:
I believe this is a double definition.
'play' is the first definition.
(I know this)
'the singer' is the second definition.
(lark is a kind of birdanimal)
'for' is the link.
(Other definitions for lark that I've seen before include "what one may get up to?" , "Bit of fun - early-rising bird?" , "carefree adventure" , "Mischievous game" , "Mess about" .)