Look -- a second domesticated animal catches cold (6)
I believe the answer is:
aspect
'look' is the definition.
('aspect' can be a synonym of 'look')
'a second domesticated animal catches cold' is the wordplay.
'a second' becomes 'as' (I've seen this in other clues**).
'domesticated animal' becomes 'pet' (I've seen this before).
'catches' indicates putting letters inside.
'cold' becomes 'c' (eg on taps).
'pet' placed around 'c' is 'pect'.
'as'+'pect'='ASPECT'
(Other definitions for aspect that I've seen before include "Visual effect" , "Particular or distinct element, of a problem say" , "front" , "Scene, panorama" , "Vista,panorama" .)