No rubbish dumping close to a lake (7)
I believe the answer is:
refusal
'no' is the definition.
(refusing is saying no)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for refusal that I've seen before include "Indication of unwillingness (to do something)" , "Rebuff" , "The turning down of a request" , "Turning-down; denial" , "regrets?" .)