Drive finishing early, blocked by one stupid dead end (7)
I believe the answer is:
impasse
'dead end' is the definition.
(synonyms)
'drive finishing early blocked by one stupid' is the wordplay.
'drive' becomes 'impel' (I've seen this before).
'finishing early' means to remove the last letter.
'blocked by' indicates putting letters inside (I've seen this in other clues).
'one stupid' becomes 'ass' (term for a stupid person).
'impel' with its last letter taken off is 'impe'.
'impe' going around 'ass' is 'IMPASSE'.
(Other definitions for impasse that I've seen before include "Stalemate situation" , "Standstill" , "I permit no further progress" , "Dead end" , "Inescapable perdicament, dilemma" .)