Seaside resort starts to restrict hosing your lawn (4)
I believe the answer is:
rhyl
'seaside resort' is the definition.
'starts to restrict hosing your lawn' is the wordplay.
'starts to' says to take the initial letters.
The first letters of 'restrict hosing your lawn' is 'RHYL'.
(Other definitions for rhyl that I've seen before include "Welsh location" , "Clwyd resort" , "North Welsh resort" , "N Wales resort" , "Welsh resort near Colwyn Bay" .)