A right idiot undermining hospital creates worry (6)
I believe the answer is:
harass
'worry' is the definition.
(thesaurus)
'a right idiot undermining hospital' is the wordplay.
'right' becomes 'r' (common abbreviation).
'idiot' becomes 'ass' (I've seen this before**).
'undermining' is a charade indicator (letters next to each other).
'hospital' becomes 'h'.
'a'+'r'+'ass'='arass'
'arass' put after 'h' is 'HARASS'.
'creates' acts as a link.
(Other definitions for harass that I've seen before include "bug" , "Pester constantly" , "Constantly intimidate" , "Continually torment" , "Disturb < badger" .)