Trailblazer, one plugging seaside attraction (7)
I believe the answer is:
pioneer
'trailblazer' is the definition.
(both can mean an innovator)
'one plugging seaside attraction' is the wordplay.
'plugging' means one lot of letters goes inside another (I've seen this in other clues).
'seaside attraction' becomes 'pier' (structure by the sea).
'one' placed into 'pier' is 'PIONEER'.
(Other definitions for pioneer that I've seen before include "Groundbreaker" , "Innovator; early settler" , "Open up an area" , "Ripe one (anag.)" , "first time in the field" .)