Writer experienced upset (4-3)
I believe the answer is:
felt tip
'writer' is the definition.
(a felt tip pen is something which writes)
'experienced upset' is the wordplay.
'experienced' becomes 'felt' ('feel' can be a synonym of 'experience').
'upset' becomes 'tip' (I've seen this in another clue).
'felt'+'tip'='FELT-TIP'
(Other definitions for felt tip that I've seen before include "writer" , "Type of pen" , "Variety of pen" , "(Pen with) fibre point" .)