trapping (9)
(Other definitions for catching that I've seen before include "Getting hold of or becoming infected" , "Attractive - infectious" , "getting infectious" , "Snaring" , "Seizing" .)
'trapping' is the definition.
('ensnare' can be a synonym of 'trap')
This is the entire clue.
(Another definition for ensnaring that I've seen is " Catching".)