It’s significant there are two of them outside a gambling centre (6)
I believe the answer is:
emblem
'it's significant there' is the definition.
I can't judge whether this definition defines the answer.
'two of them outside a gambling centre' is the wordplay.
'two of' says to double the letters (I've seen 'two' mean this).
'them' becomes 'em'.
'outside' means one lot of letters goes inside another.
'centre' says to take the centre.
The middle letters of 'gambling' are 'bl'.
'em' doubled is 'emem'.
'emem' enclosing 'bl' is 'EMBLEM'.
'are' is the link.
Can you help me to learn more?
(Other definitions for emblem that I've seen before include "Symbolic representation on badge etc" , "Symbol, representing a country say" , "Badge or representative device" , "Crest or insignia" , "Symbol, representative device" .)