Turn on Hospital department nursing sour criminal (6)
I believe the answer is:
arouse
'turn on' is the definition.
(I've seen this before)
'hospital department nursing sour criminal' is the wordplay.
'hospital department' becomes 'ae' (A&E, Accident & Emergency).
'nursing' means one lot of letters goes inside another.
'criminal' indicates anagramming the letters.
'sour' is an anagram of 'rous'.
'ae' placed around 'rous' is 'AROUSE'.
(Other definitions for arouse that I've seen before include "Energise" , "Stimulate or excite" , "Wake or stir up" , "Incite or stimulate" , "Awake from sleep" .)