Bears witness to cycling examination taken (7)
I believe the answer is:
attests
'bears witness' is the definition.
('attest' can be a synonym of 'bear witness')
'cycling examination taken' is the wordplay.
'cycling' becomes 'ats' (I can't explain this - if you can you should give a lot more credence to this answer).
'examination' becomes 'test' (synonyms).
'taken' is an insertion indicator.
'ats' placed around 'test' is 'ATTESTS'.
'to' is the link.
Can you help me to learn more?
(Other definitions for attests that I've seen before include "Authenticates or affirms to be true" , "Bears witness" , "Confirms" , "Sat test (anag.)" , "Gives evidence in court" .)