Swimmer no longer available to get cap (4,3)
I believe the answer is:
seal off
'cap' is the definition.
Although both the answer and definition are verbs in their base form, I can't understand how one could define the other.
'swimmer no longer available' is the wordplay.
'swimmer' becomes 'seal' (I can't explain this - if you can you should believe this answer much more).
'no longer available' becomes 'off' (I've seen this before).
'seal'+'off'='SEAL OFF'
'to get' acts as a link.
Can you help me to learn more?
(Other definitions for seal off that I've seen before include "Block completely" , "Allow nothing in or out of (an area)" , "Completely isolate (an area)" , "Put a barrier around" .)