Deal in lamps and signals (7-6)
I believe the answer is:
traffic-lights
'signals' is the definition.
(traffic light is a kind of signal)
'deal in lamps' is the wordplay.
'deal in' becomes 'traffic' (trafficking is a kind of dealing in).
'lamps' becomes 'lights' (I've seen this before).
'traffic'+'lights'='TRAFFIC-LIGHTS'
'and' is the link.
(Other definitions for traffic-lights that I've seen before include "Illuminated road signals" , "Road feature" .)