Inspect contents of intravenous cannulas (4)
I believe the answer is:
scan
'inspect' is the definition.
(to scan is to inspect or examine)
'contents of intravenous cannulas' is the wordplay.
'contents of' indicates a hidden word.
'SCAN' is hidden within 'intravenous cannulas'.
(Other definitions for scan that I've seen before include "Examine (to transmit)" , "Look over (in order to copy?)" , "Peruse, scrutinise" , "Traverse with a detector" , "Perusal" .)