Depression, after initially fading, is difficult (5)
I believe the answer is:
rough
'difficult' is the definition.
(similar in meaning)
'depression after initially fading' is the wordplay.
'depression' becomes 'trough' (trough is a kind of depression).
'after initially fading' means to remove the first letter (the initial fades away).
'trough' with its first letter taken off is 'ROUGH'.
'is' acts as a link.
(Other definitions for rough that I've seen before include "Rasping" , "general" , "Hard - coarse - inexact" , "Boisterous - thug" , "Nasty" .)