Margaret turns up with the treasure (3)
I believe the answer is:
gem
'the treasure' is the definition.
(synonyms)
'margaret turns up' is the wordplay.
'margaret' becomes 'Meg' (short for Margaret).
'turns up' says the letters should be written in reverse.
'meg' in reverse letter order is 'GEM'.
'with' is the link.
(Other definitions for gem that I've seen before include "Diamond, ruby, or emerald" , "A jewel of an Orangeman" , "Setter might bed this" , "Valuable stone" , "Treasured person" .)