Set layer round a road (6)
I believe the answer is:
harden
'set' is the definition.
(I've seen this before)
'layer round a road' is the wordplay.
'layer' becomes 'hen' (animal which lays eggs).
'round' indicates putting letters inside.
'road' becomes 'rd' (abbreviation).
'a'+'rd'='ard'
'hen' enclosing 'ard' is 'HARDEN'.
(Other definitions for harden that I've seen before include "Become less sympathetic" , "Small fly" , "Set; become tougher" , "Become stronger or firmer" , "Temper, steel say" .)