Equip with ecstasy. In one way a dominating influence (5)
I believe the answer is:
reign
'a dominating influence' is the definition.
'reign' can be an answer for 'influence' (thesaurus). I am not sure about the 'a dominating' bit.
'equip with ecstasy in one way' is the wordplay.
'equip with' becomes 'rig' (rigging is a kind of equiping. I am not sure about the 'with' bit.).
'ecstasy' becomes 'E' (informal term for the drug).
'in' is an insertion indicator.
'one way' becomes 'n' (Compass direction - North).
'rig' going around 'e' is 'reig'.
'reig'+'n'='REIGN'
Can you help me to learn more?
(Other definitions for reign that I've seen before include "Rule as king or queen" , "Wield the sceptre" , "Sit on a throne" , "Control" , "Hold sway, rule" .)