Fit blue plastic around gold -- lovely (9)
I believe the answer is:
beautiful
'lovely' is the definition.
('beautiful' can be similar in meaning to 'lovely')
'fit blue plastic around gold' is the wordplay.
'plastic' is an anagram indicator (plastic can mean easily moulded).
'around' means one lot of letters goes inside another.
'gold' becomes 'au' (Au is the chemical symbol for gold).
'fit'+'blue'='fitblue'
'fitblue' anagrammed gives 'betiful'.
'betiful' enclosing 'au' is 'BEAUTIFUL'.
(Other definitions for beautiful that I've seen before include "Comely" , "Pulchritudinous, gorgeous" , "Fine" , "Very pleasing to the senses" , "Aesthetically very pleasing" .)