Somewhat dreary task upset lecherous fellow (5)
I believe the answer is:
satyr
'lecherous fellow' is the definition.
'satyr' can be an answer for 'fellow' (I have seen 'oversexed fellow' mean 'satyr' so perhaps 'fellow' could also mean 'satyr'). I'm not sure about the 'lecherous' bit.
'somewhat dreary task upset' is the wordplay.
'somewhat' says the answer is hidden in the clue.
'upset' says the letters should be written in reverse.
'rytas' is hidden in the letters of 'dreary task'.
'rytas' in reverse letter order is 'SATYR'.
Can you help me to learn more?
(Other definitions for satyr that I've seen before include "Pursuer of nymph" , "Mythological woodland deity" , "Classical deity" , "Mythical woodland god or grossly lustful man" , "Greek sylvan deity" .)