Girl has weight to declare (8)
I believe the answer is:
announce
'declare' is the definition.
(I know that declare can be written as announce)
'girl has weight' is the wordplay.
'girl' becomes 'ann' (woman's name).
'has' means one lot of letters go next to another.
'weight' becomes 'ounce' (unit of weight).
'ann'+'ounce'='ANNOUNCE'
'to' is the link.
(Other definitions for announce that I've seen before include "say" , "Reveal" , "Formally declare" , "Give public notice to" , "Make known officially" .)