What king does with regulations (5)
I believe the answer is:
rules
'regulations' is the definition.
('rule' can be a synonym of 'regulation')
'what king does' is the wordplay.
I cannot quite understand how this works, but
'king' could be 'r' (abbreviation for rex, king in Latin) and 'r' is located in the answer.
The remaining letters 'ules' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'with' acts as a link.
Can you help me to learn more?
(Other definitions for rules that I've seen before include "governments" , "Reigns" , "Conventions" , "Is king" , "Governs; regulations" .)