Key to price when nude eating fish (3,4)
I believe the answer is:
bar code
'key to price' is the definition.
I can't tell whether this defines the answer.
'nude eating fish' is the wordplay.
'nude' becomes 'bare' (synonyms).
'eating' means one lot of letters goes inside another.
'fish' becomes 'cod' (cod is a kind of fish).
'bare' going around 'cod' is 'BAR CODE'.
'when' is the link.
Can you help me to learn more?
(Other definitions for bar code that I've seen before include "Rulebook for lawyers maybe" , "Stock item marker" , "Brocade (anag.)" , "Stock control marking" , "Machine-readable arrangement of parallel lines on product" .)