Poem about Spanish gentleman abroad is unlike any other (3,3,3)
I believe the answer is:
odd one out
'unlike any other' is the definition.
(unlike the rest)
'poem about spanish gentleman abroad' is the wordplay.
'poem' becomes 'ode' (ode is a kind of poem).
'about' is an insertion indicator.
'spanish gentleman' becomes 'don' (formal term of address for a man in Spanish).
'abroad' becomes 'out' (abroad can mean away or out).
'ode' going around 'don' is 'oddone'.
'oddone'+'out'='ODD ONE OUT'
'is' is the link.
(Other definitions for odd one out that I've seen before include "Different individual" , "exception" , "Individualist" , "Thing or person contrasting with others" .)