Pleased with an extraordinary walk by the seaside (9)
I believe the answer is:
esplanade
'walk by the seaside' is the definition.
(area for walking by the sea)
'pleased with an extraordinary' is the wordplay.
'with' says to put letters next to each other.
'extraordinary' indicates an anagram.
'pleased' put after 'an' is 'anpleased'.
'anpleased' anagrammed gives 'ESPLANADE'.
(Other definitions for esplanade that I've seen before include "Promenade" , "Open, level space for walks or drives" , "A leap ends (anag) - seaside feature" , "front" , "Walkway beside the seashore" .)