Provoked with rash outcome possibly (7)
I believe the answer is:
'provoked' is the definition.
(nettling is a kind of provoking)
'with rash outcome possibly' is the wordplay.
'with' says to put letters next to each other.
'rash' becomes 'nettle rash' (nettle rash is a kind of rash).
'outcome possibly' becomes 'd' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'nettle' next to 'd' is 'NETTLED'.
Can you help me to learn more?
(Other definitions for nettled that I've seen before include "Annoyed, irritated" , "Provoked" , "Annoyed as by stinging plant" , "Irritated as by stinging plant" , "becomes annoyed" .)