Showing no restraint, boy grabs daughter (6)
I believe the answer is:
wildly
'showing no restraint' is the definition.
'boy grabs daughter' is the wordplay.
'boy' becomes 'willy' (**).
'grabs' is an insertion indicator.
'daughter' becomes 'd'.
'willy' enclosing 'd' is 'WILDLY'.
(Other definitions for wildly that I've seen before include "With enthusiasm" , "Recklessly" , "In a way that lacks discipline or restraint" .)