Fancy lace covering one girl (5)
I believe the answer is:
'girl' is the definition.
'fancy lace covering one' is the wordplay.
'fancy' indicates an anagram.
'covering' means one lot of letters goes inside another.
'one' becomes 'i' (Roman numeral).
'lace' is an anagram of 'cela'.
'cela' placed around 'i' is 'CELIA'.
(Other definitions for celia that I've seen before include "Rosalind's cousin" , "Frederick's daughter" , "lady" , "Character in Tales from Shakespeare" , "Daughter to Frederick" .)