A marksman will use this sort of gift horse (9)
I believe the answer is:
foresight
'a marksman will use this sort' is the definition.
The answer and definition can be both human attributes as well as being singular nouns.
Maybe there's an association between them I don't understand?
'of gift horse' is the wordplay.
'of' is an anagram indicator (the answer comes from or 'of' the letters).
'gift'+'horse'='gifthorse'
'gifthorse' anagrammed gives 'FORESIGHT'.
Can you help me to learn more?
(Other definitions for foresight that I've seen before include "Vision" , "Prescience" , "Power of prediction" , "Ability to anticipate" , "Prudence" .)