Foul sailor almost exhausted saving old Mrs Harker (10)
I believe the answer is:
abominable
'foul' is the definition.
(synonyms)
'sailor almost exhausted saving old mrs harker' is the wordplay.
I cannot really see how this works, but
'sailor' could be 'ab' (abbreviation for able seaman) and 'ab' is found in the answer.
'old' could be 'o' (common abbreviation eg in OE for Old English) and 'o' is present in the answer.
'mrs' could be 'mina' and 'mina' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for abominable that I've seen before include "Hateful" , "Odious" , "Atrocious" , "Causing moral revulsion" , "Very bad, terrible" .)