Inhale and swim round about (7)
I believe the answer is:
breathe
'inhale' is the definition.
(to inhale is to breathe in)
'swim round about' is the wordplay.
'swim' becomes 'bathe' (bathe can mean to swim).
'round' indicates putting letters inside.
'about' becomes 're' ('re' means regarding or about).
'bathe' enclosing 're' is 'BREATHE'.
'and' acts as a link.
(Other definitions for breathe that I've seen before include "wheeze" , "eg Inhale" , "Tell" , "Draw air into, and expel out of, the lungs" , "Inhale and exhale" .)