Miserable whistle-blower's first gagged (8)
I believe the answer is:
wretched
'miserable' is the definition.
(I know that miserable can be written as wretched)
'whistle-blower's first gagged' is the wordplay.
'whistle-blower's' becomes 'w' (this might be a standard abbreviation which I don't know about).
'first' says to put letters next to each other.
'gagged' becomes 'retched' (retch can mean to gag or clear one's throat).
'w'+'retched'='WRETCHED'
Can you help me to learn more?
(Other definitions for wretched that I've seen before include "Very unhappy, miserable" , "misery" , "Abject" , "awful" , "Pitiful" .)