Fly low with daring (10)
I believe the answer is:
bluebottle
'fly' is the definition.
(bluebottle is a kind of fly)
'low with daring' is the wordplay.
'low' becomes 'blue' (both can mean unhappy).
'with' means one lot of letters go next to another.
'daring' becomes 'bottle'.
'blue'+'bottle'='BLUEBOTTLE'
(Other definitions for bluebottle that I've seen before include "Fly - policeman" , "Officer" , "Large fly -- wild cornflower" , "Copper - fly" , "Flier" .)