Ruby, perhaps unexpectedly, gets on with me (8)
I believe the answer is:
gemstone
'ruby perhaps' is the definition.
(ruby is a kind of gemstone)
'unexpectedly gets on with me' is the wordplay.
'unexpectedly' indicates anagramming the letters.
'with' says to put letters next to each other.
'gets'+'on'='getson'
'getson' put after 'me' is 'megetson'.
'megetson' anagrammed gives 'GEMSTONE'.
(Other definitions for gemstone that I've seen before include "Emerald or ruby" , "something of great value" , "Jewel" , "Sparkler" , "Eg, sapphire" .)