Wasted without protection, with sailors at the back (6)
I believe the answer is:
astern
'at the back' is the definition.
(I've seen this before)
'wasted without protection with sailors' is the wordplay.
'without protection' indicates the central letters (no outside letters).
'with' says to put letters next to each other.
'sailors' becomes 'RN' (abbreviation for Royal Navy).
The middle letters of 'wasted' are 'aste'.
'aste'+'rn'='ASTERN'
(Other definitions for astern that I've seen before include "following behind vessel" , "(In relation to ship) behind" , "Towards the rear of boat" , "Aft" , "back for sailors" .)