Engineer cross after permit is rejected (7)
I believe the answer is:
Here is my best explanation:
'engineer' is the definition.
'cross after permit is rejected' is the subsidiary indication.
'cross' becomes 'ford' (fording is a kind of crossing**).
'after' says to put letters next to each other.
'permit' becomes 'let' ('let' can be a synonym of 'permit').
'is rejected' says the letters should be written backwards.
'let' backwards is 'tel'.
'ford' after 'tel' is 'telford'.
(Other definitions for telford that I've seen before include "Salop. town; engineer", "Thomas -, eighteenth - nineteenth century Scottish engineer", "Thomas - Sc. engineer", "Town in Shropshire", "Scottish engineer; town in Shropshire" and "Thomas -, eighteen to nineteenth century Scots civil engineer".)