Old priest the Spanish one (3)
I believe the answer is:
eli
'old priest' is the definition.
(Biblical character)
'the spanish one' is the wordplay.
'the spanish' becomes 'el' ('the' in Spanish).
'one' becomes 'i' (Roman numeral).
'el'+'i'='ELI'
(Other definitions for eli that I've seen before include "Religious character" , "Man" , "Shiloh priest (Bible)" , "- Wallach, US actor" , "Highest priest at Shiloh" .)