Worth a shot, before wavering, to blow one's top (5,1,6)
I believe the answer is:
throw a wobbly
'blow one's top' is the definition.
(both can mean to become very angry)
'worth a shot before wavering' is the wordplay.
'shot' indicates an anagram.
'before' says to put letters next to each other.
'wavering' becomes 'wobbly' (both can mean unsteady).
'worth'+'a'='wortha'
'wortha' with letters rearranged gives 'throwa'.
'throwa'+'wobbly'='THROW A WOBBLY'
'to' acts as a link.
(Other definitions for throw a wobbly that I've seen before include "Go ballistic" , "Suddenly blow a fuse" , "Have a tantrum (colloq.)" , "Have a fit" , "Have a (jelly-like?) tantrum" .)