Gives swimmer indication that a deal has been agreed (9)
I believe the answer is:
handshake
'indication that a deal has been agreed' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Maybe you can see an association between them that I don't see?
'gives swimmer' is the wordplay.
'gives' becomes 'hands' ('hand' can be a synonym of 'give').
'swimmer' becomes 'hake' (type of fish).
'hands'+'hake'='HANDSHAKE'
Can you help me to learn more?
(Other definitions for handshake that I've seen before include "introductory offer?" , "Form of greeting" , "Gesture of greeting or of agreeing a deal" , "Physical greeting" , "acknowledgment" .)