Needs a slap when drunk walks by the sea (10)
I believe the answer is:
esplanades
'walks by the sea' is the definition.
(an esplanade is a walkway by the sea)
'needs a slap when drunk' is the wordplay.
'when drunk' is an anagram indicator (a drunken or disorderly form of the letters).
'needs'+'a'+'slap'='needsaslap'
'needsaslap' with letters rearranged gives 'ESPLANADES'.
(Other definitions for esplanades that I've seen before include "seaside walks" , "go to seaside resorts for such" , "Seafront walks" , "Places to stroll" .)