Is unable to swing round (4)
I believe the answer is:
cant
This clue is a double definition.
'is unable to' is the first definition.
(can't)
'swing round' is the second definition.
(thesaurus)
(Other definitions for cant that I've seen before include "Negative-sounding hypocrisy" , "Incline, slope" , "Lacks ability" , "tilt" , "List" .)