Place to gamble with mature, Damascene conversion (9,6)
I believe the answer is:
amusement arcade
'place to gamble' is the definition.
(place with gambling machines)
'with mature damascene conversion' is the wordplay.
'with' means one lot of letters go next to another.
'conversion' indicates an anagram.
'mature'+'damascene' is 'maturedamascene'.
'maturedamascene' with letters rearranged gives 'AMUSEMENT ARCADE'.
(Other definitions for amusement arcade that I've seen before include "gambling joint" , "Where to find games machines" , "kids might have fun here" , "gambling haunt" .)