One of five, in the borders of Europe, like a horse (6)
I believe the answer is:
equine
'like a horse' is the definition.
(I've seen this before)
'one of five in the borders of europe' is the wordplay.
'one of five' becomes 'quin' (I've seen this before).
'in' indicates putting letters inside.
'the borders of' says to hollow out the word (remove centre letters).
'europe' with its middle taken out is 'ee'.
'quin' inserted within 'ee' is 'EQUINE'.
(Other definitions for equine that I've seen before include "Like a horse" , "like knight?" , "Horse-like" , "like Black Beauty" , "Like horses" .)