Check a bit of boisterous temper (4)
I believe the answer is:
stem
'check' is the definition.
(both can mean to control or stop)
'a bit of boisterous temper' is the wordplay.
'a bit of' indicates a hidden word.
'STEM' is hidden within 'boisterous temper'.
(Other definitions for stem that I've seen before include "Stanch" , "Stop or slow the flow of" , "'Stalk, shank (4)'" , "Ski turn and plant support" , "root" .)