Disease from Congress allowed to spike (8)
I believe the answer is:
stiletto
'spike' is the definition.
(thesaurus)
'disease from congress allowed to' is the wordplay.
'disease from congress' becomes 'STI' (sexually transmitted infection, congress means sex).
'allowed' becomes 'let' (to let is to allow or permit).
'sti'+'let'+'to'='STILETTO'
(Other definitions for stiletto that I've seen before include "Dagger with slender blade" , "Type of heel" , "High-heeled shoe" , "Item of footwear" , "Long dagger" .)