Gloomy linesman on the way up (4)
I believe the answer is:
drab
'gloomy' is the definition.
(I've seen this before)
'linesman on the way up' is the wordplay.
'linesman' becomes 'bard' (bard is a kind of poet).
'on the way up' says the letters should be written backwards.
'bard' written backwards gives 'DRAB'.
(Other definitions for drab that I've seen before include "Dull light brown colour" , "Dingy - shabby" , "Dull and monotonous" , "Lacking brightness or colour" , "Tedious" .)