Model former politician protecting key city transport (9)
I believe the answer is:
exemplary
'model' is the definition.
(I know that model can be written as exemplary)
'former politician protecting key city transport' is the wordplay.
'former' becomes 'ex' (prefix meaning former or onetime).
'politician' becomes 'MP' (Member of Parliament).
'protecting' means one lot of letters goes inside another (inserted letters are held or protected).
'key' becomes 'e' (a musical key).
'city transport' becomes 'lary' (I can't explain this - if you can you should believe this answer much more).
'ex'+'mp'='exmp'
'exmp' going around 'e' is 'exemp'.
'exemp'+'lary'='EXEMPLARY'
Can you help me to learn more?
(Other definitions for exemplary that I've seen before include "Outstandingly good, others should imitate" , "Serving as a good model" , "Ideal" , "Worthy of imitation" , "Perfect" .)