Only one pound in the red, but unhappy (5)
I believe the answer is:
riled
'unhappy' is the definition.
The answer and definition are different parts of speech. However, adjectives and past participle verbs sometimes define each other.
'only one pound in the red' is the wordplay.
'only one' becomes 'i' (Roman numeral. I am not sure about the 'only' bit.).
'pound' becomes 'L' (the pound sign is based on an L).
'in' is an insertion indicator.
'i'+'l'='il'
'il' placed into 'red' is 'RILED'.
'but' acts as a link.
Can you help me to learn more?
(Other definitions for riled that I've seen before include "Made angry" , "Annoyed" , "get angry" , "Irritated, provoked" , "Nettled" .)