Leading parade miles away (4)
I believe the answer is:
arch
'leading' is the definition.
(e.g. in arch-enemy)
'parade miles away' is the wordplay.
'parade' becomes 'march' ('march' can be a synonym of 'parade').
'miles' becomes 'm' (common abbreviation).
'away' is a deletion indicator.
'march' with 'm' removed is 'ARCH'.
(Other definitions for arch that I've seen before include "Cunning; span" , "Supporting structure" , "not to go straight?" , "Affectedly playful in curved manner" , "Curve that spans an opening" .)