Dominates certain conventions (5)
I believe the answer is:
rules
This clue could be a double definition.
'dominates' is the first definition.
('rule' can be a synonym of 'dominate')
'certain conventions' is the second definition.
'rules' can be an answer for 'conventions' ('rule' can be a synonym of 'convention'). I am unsure of the 'certain' bit.
Can you help me to learn more?
(Other definitions for rules that I've seen before include "Governs; regulations" , "Is king" , "Regulations, precepts" , "controls" , "strips" .)