Big copper's ex gets kiss (8)
I believe the answer is:
osculate
'kiss' is the definition.
('osculate' can be a synonym of 'kiss')
'big copper's ex' is the wordplay.
'big' becomes 'os'.
'copper' becomes 'cu' (chemical symbol).
'ex' becomes 'late' (I've seen this in other clues).
'os'+'cu'+'late'='OSCULATE'
'gets' is the link.
(Other definitions for osculate that I've seen before include "Locate us in order to kiss formally" , "O, cute Sal could kiss" , "Kiss pretentiously?" , "Kiss in lacteous way" , "Locate us engaged in pretentious kiss" .)