Onset of terrible pain in artist’s windpipe (7)
I believe the answer is:
trachea
'windpipe' is the definition.
(synonyms)
'onset of terrible pain in artist's' is the wordplay.
'onset of' says to take the initial letters.
'pain' becomes 'ache' (ache is a kind of pain).
'in' means one lot of letters goes inside another.
'artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
The initial letter of 'terrible' is 't'.
'ache' put inside 'ra' is 'rachea'.
't'+'rachea'='TRACHEA'
(Other definitions for trachea that I've seen before include "Tube carrying air to the lungs" , "Breathing tube" , "air passage" , "pipe" , "body part" .)