Maybe bishop climbs on top ... of cathedral, that is (6)
I believe the answer is:
namely
'that is' is the definition.
(I've seen this before)
'maybe bishop climbs on top of cathedral' is the wordplay.
'maybe bishop' becomes 'man' (I can't explain this - if you can you should believe this answer much more).
'climbs' says the letters should be written backwards.
'on top of' means one lot of letters go next to another.
'cathedral' becomes 'ely' (cathedral city in Cambridgeshire).
'man' back-to-front is 'nam'.
'nam'+'ely'='NAMELY'
Can you help me to learn more?
(Other definitions for namely that I've seen before include "Videlicet" , "Viz" , "to wit" , "That is to say, specifically" , "Old especially" .)