Socialist leader frequently showing temper (6)
I believe the answer is:
soften
'temper' is the definition.
(I've seen this before)
'socialist leader frequently' is the wordplay.
'leader' suggests taking the first letters.
'frequently' becomes 'often' ('often' can be a synonym of 'frequently').
The initial letter of 'socialist' is 's'.
's'+'often'='SOFTEN'
'showing' is the link.
(Other definitions for soften that I've seen before include "Make more plastic" , "Become gentler" , "Appease" , "Temper" , "Make less hard or become less severe" .)