Extreme anger starts to worry receptionist at hospital (5)
I believe the answer is:
wrath
'extreme anger' is the definition.
(I've seen this before)
'starts to worry receptionist at hospital' is the wordplay.
'starts to' indicates taking the first letters.
'hospital' becomes 'h'.
The initial letters of 'worry receptionist' is 'wr'.
'wr'+'at'+'h'='WRATH'
(Other definitions for wrath that I've seen before include "Intense anger" , "head in Scotland" , "Fury" , "Failure to keep cool" , "Angry indignation" .)