Pioneer at least did this in past — a clever eccentric (5,6)
I believe the answer is:
space travel
'pioneer at least did this' is the definition.
The definition suggests a singular noun which matches the answer.
'past a clever eccentric' is the wordplay.
'eccentric' indicates anagramming the letters.
'past'+'a'+'clever'='pastaclever'
'pastaclever' is an anagram of 'SPACE TRAVEL'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for space travel that I've seen before include "Voyaging beyond earth's atmosphere" , "a journey out of this world" , "Journeying afar" , "Journeys out of this world" .)