Act in accordance with the rules (6)
I believe the answer is:
comply
'act in accordance with the rules' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for comply that I've seen before include "Yield to the wishes of another" , "Agree - obey orders" , "Conform to rules" , "Toe the line" , "Extra runs; farewells" .)