Opportunity to wind up German leader, perhaps (10)
I believe the answer is:
chancellor
'german leader perhaps' is the definition.
(the head of the German government is a chancellor)
'opportunity to wind up' is the wordplay.
'opportunity' becomes 'chance' (synonyms).
'to wind' becomes 'roll' ('roll' can be a synonym of 'wind').
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'roll' written backwards gives 'llor'.
'chance'+'llor'='CHANCELLOR'
(Other definitions for chancellor that I've seen before include "See 8" , "Government leader" , "chief minister" , "Govt. finance minister" , "Titular university head" .)