Extremely dreary man about town (5)
I believe the answer is:
dandy
'man about town' is the definition.
(I've seen this before)
I don't understand the remainder of the clue.
(Other definitions for dandy that I've seen before include "Old comic" , "Stylish dresser" , "one of stylish ways" , "Showy dresser" , "Marathon running strips" .)