Trick by unwanted surfer endlessly achieving dominance (7)
I believe the answer is:
control
'dominance' is the definition.
('control' can be a synonym of 'dominance')
'trick by unwanted surfer endlessly' is the wordplay.
'trick' becomes 'con' (I've seen this before).
'by' is a charade indicator (letters next to each other).
'unwanted surfer' becomes 'troll' (term for a malicious person surfing the internet).
'endlessly' means to remove the last letter.
'troll' with its last letter taken off is 'trol'.
'con'+'trol'='CONTROL'
'achieving' is the link.
(Other definitions for control that I've seen before include "Handle, operate" , "Check" , "Regulation" , "Command, regulate" , "domination" .)