Flying seaplane initially disrupts seaside walk (9)
I believe the answer is:
esplanade
'seaside walk' is the definition.
(I've seen this before)
'flying seaplane initially disrupts' is the wordplay.
'flying' indicates anagramming the letters.
'initially' says to take the initial letters.
The initial letter of 'disrupts' is 'd'.
'seaplane'+'d'='seaplaned'
'seaplaned' is an anagram of 'ESPLANADE'.
(Other definitions for esplanade that I've seen before include "Open, level space for walks or drives" , "Level seashore walkway" , "Seafront walk" , "Seaside walkway" , "Promenade" .)