He's gloomy about Englishman returning (5)
I believe the answer is:
moper
'he's gloomy' is the definition.
(someone who mopes around)
'about englishman returning' is the wordplay.
'about' becomes 're' (regarding).
'englishman' becomes 'pom' (pom is a kind of englishman).
'returning' shows that the letters should be reversed in order.
're'+'pom'='repom'
'repom' back-to-front is 'MOPER'.
(Other definitions for moper that I've seen before include "Weary Willie" , "One who's depressed" .)