Old county girl needing surgery (5)
I believe the answer is:
salop
'old county' is the definition.
(I've seen this before)
'girl needing surgery' is the wordplay.
'girl' becomes 'sal' (feminine given name).
'needing' is a charade indicator (letters next to each other).
'surgery' becomes 'op' (short for operation).
'sal'+'op'='SALOP'
(Other definitions for salop that I've seen before include "Alternative name for the county of Shropshire" , "Telford here" , "Shropshire (abbreviation)" , "Shropshire (abbr.)" , "Shropshire in short" .)