Pretty girl introduced into company (6)
I believe the answer is:
comely
'pretty' is the definition.
(comely can mean pretty or attractive)
'girl introduced into company' is the wordplay.
'girl' becomes 'Mel' (short for Melanie).
'introduced into' means one lot of letters goes inside another.
'company' becomes 'coy' (I can't justify this - if you can you should believe this answer much more).
'mel' going inside 'coy' is 'COMELY'.
Can you help me to learn more?
(Other definitions for comely that I've seen before include "Archaic word for good-looking, say maidens" , "Very pleasing to the eye, as Dev's maidens perhaps" , "Good-looking, old usage as of maiden" , "Good-looking - like old-time maidens?" , "Pleasant looking" .)