One light put up in shop (4)
I believe the answer is:
deli
'in shop' is the definition.
(I've seen this before)
'one light put up' is the wordplay.
'one' becomes 'i' (Roman numeral).
'light' becomes 'led' (light-emitting diode).
'put up' says the letters should be written backwards.
'i'+'led'='iled'
'iled' backwards is 'DELI'.
(Other definitions for deli that I've seen before include "Shop selling processed food products" , "Shop with unusual foods" , "Fine foods shop" , "place to buy food" , "food outlet" .)