Put an edge on things at Southend in the rain (4)
I believe the answer is:
whet
'put an edge on' is the definition.
(I've seen this in another clue)
'at southend in the rain' is the wordplay.
I cannot quite see how this works, but
an anagram of 'the' is 'het' which is present in the answer.
A single letter 'w' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
'things' acts as a link.
Can you help me to learn more?
(Other definitions for whet that I've seen before include "Sharpen the blade of (a tool/weapon)" , "Make more acute" , "Sharpen by rubbing" , "Arouse" , "Make keen" .)