Time travel could be cool in the beginning (8)
I believe the answer is:
interval
'cool in the beginning' is the definition.
The answer and definition can be both human attributes as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'time travel could be' is the wordplay.
'time' becomes 'in' (I can't explain this - if you can you should believe this answer much more).
'could be' is an anagram indicator.
'travel' with letters rearranged gives 'terval'.
'in'+'terval'='INTERVAL'
Can you help me to learn more?
(Other definitions for interval that I've seen before include "Pause, break" , "Intervening time" , "Hiatus" , "Short break" , "Pause in middle of performance" .)