To illustrate, keep serving a writ on flight (8)
I believe the answer is:
stairway
'flight' is the definition.
(flights of stairs)
'to illustrate keep serving a writ' is the wordplay.
'to illustrate' becomes 'say' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'keep' indicates putting letters inside.
'serving' is an anagram indicator.
'a'+'writ'='awrit'
'awrit' with letters rearranged gives 'tairw'.
'say' enclosing 'tairw' is 'STAIRWAY'.
'on' is the link.
Can you help me to learn more?
(Other definitions for stairway that I've seen before include "A flight of fixed indoor steps" , "- to Heaven, Led Zeppelin song" .)