Deny special agent is going to Spain (6)
I believe the answer is:
negate
'deny' is the definition.
(thesaurus)
'special agent is going to spain' is the wordplay.
'special' indicates an anagram.
'is going to' is a charade indicator (letters next to each other).
'spain' becomes 'e' (abbreviation for Espana).
'agent' anagrammed gives 'negat'.
'negat'+'e'='NEGATE'
(Other definitions for negate that I've seen before include "Countermand" , "Deny the truth of" , "Opera by Puccini" , "Render null or disprove" , "Contradict" .)