Sailor backing ugly old woman, a despicable type (6)
I believe the answer is:
ratbag
'a despicable type' is the definition.
(a ratbag is a despicable person)
'sailor backing ugly old woman' is the wordplay.
'sailor' becomes 'tar' (term for a sailor).
'backing' says the letters should be written backwards.
'ugly old woman' becomes 'bag' (insulting term).
'tar' backwards is 'rat'.
'rat'+'bag'='RATBAG'
(Other definitions for ratbag that I've seen before include "bounder" , "Grab at (anag) - contemptible person" , "unpleasant customer" , "snake" , "One displaying bad form" .)