Get back, for instance, into the water (6)
I believe the answer is:
regain
'get back' is the definition.
(I've seen this before)
'for instance into the water' is the wordplay.
'for instance' becomes 'eg' (short for 'exempli gratia', 'for example' in Latin).
'into' indicates putting letters inside.
'the water' becomes 'rain' (rain is a kind of water).
'eg' placed within 'rain' is 'REGAIN'.
(Other definitions for regain that I've seen before include "Take back (the Ashes, for example)" , "Recover - in gear (anag)" , "Possess once more for regina" , "Recover, retrieve" , "Win back" .)