Old traitor, finally contrite, to give speech (5)
I believe the answer is:
orate
'give speech' is the definition.
(I've seen this before)
'old traitor finally contrite' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'traitor' becomes 'rat' (I've seen this before).
'finally' indicates one should take the final letters.
The final letter of 'contrite' is 'e'.
'o'+'rat'+'e'='ORATE'
'to' is the link.
(Other definitions for orate that I've seen before include "Lecture" , "Speak formally" , "Hold forth" , "Make a formal speech" , "Speak in florid style" .)