Betrayer is characteristic and engineers ship (9)
I believe the answer is:
traitress
'betrayer' is the definition.
(I know that traitress is a type of betrayer)
'characteristic and engineers ship' is the wordplay.
'characteristic' becomes 'trait' (a trait is a quality or characteristic).
'and' says to put letters next to each other.
'engineers' becomes 're' (Royal Engineers).
'ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
'trait'+'re'+'ss'='TRAITRESS'
'is' is the link.
(Other definitions for traitress that I've seen before include "False woman" , "Betrayer of her country" .)