Seeing wife infectious but not with cold (8)
I believe the answer is:
watching
'seeing' is the definition.
('watch' can be a synonym of 'see')
'wife infectious but not with cold' is the wordplay.
'wife' becomes 'w'.
'infectious' becomes 'catching' ('catching' can be similar in meaning to 'infectious').
'but not with' is a deletion indicator.
'cold' becomes 'c' (eg on taps).
'catching' with 'c' taken away is 'atching'.
'w'+'atching'='WATCHING'
(Other definitions for watching that I've seen before include "Viewing" , "Keeping an eye on" , "Observing" .)