Impasse reached after a late finish (4,3)
I believe the answer is:
dead end
'impasse' is the definition.
(synonyms)
'after a late finish' is the wordplay.
'after' says to put letters next to each other.
'a late' becomes 'dead' (I've seen this before).
'finish' becomes 'end' (synonyms).
'dead' put next to 'end' is 'DEAD-END'.
'reached' acts as a link.
This may not be correct. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for dead end that I've seen before include "Blind alley, cul-de-sac" , "going nowhere" , "Blind alley or situation without prospects" , "that's leading nowhere" , "Where no progress can be made" .)