A feeble prosecutor, so walk (7)
I believe the answer is:
alameda
'walk' is the definition.
(Spanish term for a walkway)
'a feeble prosecutor' is the wordplay.
'feeble' becomes 'lame' (lame can mean feeble or pathetic).
'prosecutor' becomes 'D.A.' (District Attorney).
'a'+'lame'+'da'='ALAMEDA'
'so' acts as a link.
(Other definitions for alameda that I've seen before include "walk in America" , "Tree-lined promenade" , "walk abroad" , "Public walk" , "Tree-lined walk (Sp.)" .)