Lira — foreign currency in Guiana circulating as means of exchange (6,6)
I believe the answer is:
lingua franca
'means of exchange' is the definition.
'lira foreign currency in guiana circulating' is the wordplay.
'lira' becomes 'l'.
'foreign currency' becomes 'franc' (I've seen this before).
'in' indicates putting letters inside.
'circulating' indicates an anagram.
'guiana' anagrammed gives 'inguaa'.
'franc' inserted within 'inguaa' is 'inguafranca'.
'l'+'inguafranca'='LINGUA FRANCA'
'as' acts as a link.
(Other definitions for lingua franca that I've seen before include "Hybrid medium of communication" , "Common language" .)