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 am not sure about this - if you are sure you should give a lot more credence to this answer).
'examination' becomes 'test' (synonyms).
'taken' is an insertion indicator.
'ats' going around 'test' is 'ATTESTS'.
'to' acts as a 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" .)