Lighter belt found in hole (3,4)
I believe the answer is:
gas lamp
'lighter' is the definition.
(I've seen this before)
'belt found in hole' is the wordplay.
'belt' becomes 'slam'.
'found in' means one lot of letters goes inside another.
'hole' becomes 'gap'.
'slam' put inside 'gap' is 'GAS-LAMP'.
(Other definitions for gas lamp that I've seen before include "Source of illumination" , "Burning source of light" , "Victorian street light" , "may be illuminating" , "Sort of light" .)