Discern contract snag (5)
I believe the answer is:
catch
I believe this is a triple definition!
'discern' is the first definition.
(thesaurus)
'contract' is the second definition.
(to catch an illness is to contract it)
'snag' is the third definition.
(I know that snag is a more specific form of the action catch)
(Other definitions for catch that I've seen before include "Snag - trap" , "Fastener on door or window" , "Arrest" , "Trap - hear - contract" , "Seize; start burning" .)