Finished, anxious - that tells you what's happened (4,5)
I believe the answer is:
past tense
'tells you what's happened' is the definition.
I can't tell whether this definition defines the answer.
'finished anxious' is the wordplay.
'finished' becomes 'past' (I've seen this in another clue).
'anxious' becomes 'tense' (I've seen this before).
'past'+'tense'='PAST TENSE'
'that' acts as a link.
Can you help me to learn more?
(Other definitions for past tense that I've seen before include "It expresses something that has happened" , "Was perhaps" , "Grammatical verb form" , "What could be perfect in a lesson of French" , "history?" .)