Upset first man getting hold of drunk girl (7)
I believe the answer is:
matilda
'girl' is the definition.
'upset first man getting hold of drunk' is the wordplay.
'upset' is a reversal indicator.
'first man' becomes 'adam' (first man in the Bible).
'getting hold of' is an insertion indicator.
'drunk' becomes 'lit' (slang term).
'adam' enclosing 'lit' is 'adlitam'.
'adlitam' reversed gives 'MATILDA'.
(Other definitions for matilda that I've seen before include "Empress Maud" , "Mother of Henry II; bushman's swag" , "Australian bushman's swag" , "See 17" , "Roald Dahl heroine" .)