Cold bottle of milk, on reflection, is what kitty loves? (6)
I believe the answer is:
catnip
'what kitty loves?' is the definition.
(catnip attracts cats)
'cold bottle of milk on reflection' is the wordplay.
'cold' becomes 'c' (eg on taps).
'bottle of milk' becomes 'pinta' (non-standard pronunciation of 'pint of').
'on reflection' shows that the letters should be reversed in order.
'pinta' reversed gives 'atnip'.
'c'+'atnip'='CATNIP'
'is' is the link.
(Other definitions for catnip that I've seen before include "flower" , "feline favourite?" , "Plant favoured by felines" , "Herb of the mint family, attractive to some pets" , "treat for kitten" .)