As in Rome to stop the Spanish getting even (5)
I believe the answer is:
equal
'even' is the definition.
(I've seen this before)
'as in rome to stop the spanish' is the wordplay.
'as in rome' becomes 'qua' (Latin word meaning 'in the role of', 'as').
'to stop' indicates putting letters inside.
'the spanish' becomes 'el'.
'qua' inserted within 'el' is 'EQUAL'.
'getting' is the link.
(Other definitions for equal that I've seen before include "Commensurate" , "Keep pace with - peer" , "The same; even" , "The same; fairly balanced" , "Fifty-fifty" .)