Somewhat important I catch lark (5)
I believe the answer is:
antic
'lark' is the definition.
(I've seen this in another clue)
'somewhat important i catch' is the wordplay.
'somewhat' indicates a hidden word.
'ANTIC' can be found hidden inside 'important i catch'.
(Other definitions for antic that I've seen before include "Absurd action" , "Prank" , "Grotesque, fantastic (archaic)" , "Eccentric once" , "Ludicrous act done for fun" .)