Hydrophobic sailor free to come round (5)
I believe the answer is:
rabid
'hydrophobic' is the definition.
(I've seen this before)
'sailor free to come round' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'free' becomes 'rid' (to be free of something is to be rid of it).
'to come round' indicates putting letters inside.
'ab' inserted within 'rid' is 'RABID'.
(Other definitions for rabid that I've seen before include "Wild" , "Frenzied" , "Fanatical - hydrophobic" , "Ferocious" , "extremist" .)