Identify with English shipmate at sea (9)
I believe the answer is:
empathise
'identify with' is the definition.
'english shipmate at sea' is the wordplay.
'english' becomes 'e' (abbreviation**).
'at sea' indicates anagramming the letters.
'shipmate' with letters rearranged gives 'mpathise'.
'e'+'mpathise'='EMPATHISE'
(Other definitions for empathise that I've seen before include "Be understanding of" , "Understand and feel as another person does - time phase (anag)" , "Have fellow-feeling for" , "Identify mentally with another person" .)