Engineer cross after permit is rejected (7)
I believe the answer is:
telford
'engineer' is the definition.
(Thomas Telford)
'cross after permit is rejected' is the wordplay.
'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 in reverse.
'let' written backwards gives '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" , "he built the Menai bridge" , "Scottish engineer; town in Shropshire" .)