Paddle when content to swim (5)
I believe the answer is:
bathe
'swim' is the definition.
(bathe can mean to swim)
'paddle when content' is the wordplay.
'paddle' becomes 'bat' (I can't justify this - if you can you should give a lot more credence to this answer).
'content' indicates the central letters.
The centre of 'when' is 'he'.
'bat'+'he'='BATHE'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for bathe that I've seen before include "Take dip in sea" , "bit of swimming" , "Swim or paddle" , "Wash, soak" , "Suffuse" .)