Lads I'm training are gloomy (6)
I believe the answer is:
dismal
'gloomy' is the definition.
(I know that gloomy can be written as dismal)
'lads i'm training' is the wordplay.
'training' indicates anagramming the letters (to train can mean to grow something into a shape).
'lads'+'im'='ladsim'
'ladsim' is an anagram of 'DISMAL'.
'are' is the link.
(Other definitions for dismal that I've seen before include "Wretched" , "Gloomy and cheerless" , "Lugubrious" , "of poor quality" , "'Depressing, grim (6)'" .)