Reluctant to acquire a horse so unkempt (6)
I believe the answer is:
shaggy
'unkempt' is the definition.
(I've seen this in another clue)
'reluctant to acquire a horse' is the wordplay.
'reluctant' becomes 'shy' (I've seen this in other clues).
'to acquire' means one lot of letters goes inside another.
'horse' becomes 'gg' (geegee or GG is a childish term for a horse).
'a'+'gg'='agg'
'shy' going around 'agg' is 'SHAGGY'.
'so' acts as a link.
(Other definitions for shaggy that I've seen before include "(Of fur) long and unkempt" , "Scooby-Doo's friend" , "Hairily unkempt" , "Very hairy, like some dog stories" , "Type of dog with story" .)