Wave behind swimmer ending on shore -- a cracker! (4-7)
I believe the answer is:
code-breaker
'a cracker' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.
'wave behind swimmer ending on shore' is the wordplay.
'wave' becomes 'breaker' (breaker is a kind of wave).
'behind' says to put letters next to each other.
'swimmer' becomes 'cod' (type of fish).
'ending on' indicates one should take the final letters.
The last letter of 'shore' is 'e'.
'cod'+'e'='code'
'breaker' put after 'code' is 'CODE-BREAKER'.
Can you help me to learn more?
(Another definition for code-breaker that I've seen is " Person employed as a cracker?".)