Pet at the chemist's, the old story (4,2,5)
I believe the answer is:
puss in boots
'old story' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.
'pet at the chemist's' is the wordplay.
'pet' becomes 'puss' (I've seen this before).
'at' becomes 'in' (synonymous in some cases - eg at school, in school).
'the chemist' becomes 'Boots' (chain of UK chemists).
'puss'+'in'+'boots'='PUSS IN BOOTS'
'the' acts as a link.
Can you help me to learn more?
(Other definitions for puss in boots that I've seen before include "Popular panto" , "Pantomime" , "Panto title" .)