Thin writer with terrible rage (6)
I believe the answer is:
meagre
'thin' is the definition.
(I've seen this before)
'writer with terrible rage' is the wordplay.
'writer' becomes 'me' (the person who wrote the clues).
'with' says to put letters next to each other.
'terrible' is an anagram indicator.
'rage' with letters rearranged gives 'agre'.
'me'+'agre'='MEAGRE'
(Other definitions for meagre that I've seen before include "Scarce - scanty" , "lacking in strength" , "Inadequate, scanty" , "Scanty, not plentiful" , "Lean; lacking in quality" .)