He was the first one on to take a look around (7)
I believe the answer is:
pioneer
'he was the' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'one on to take a look around' is the wordplay.
'one' becomes 'i' (Roman numeral).
'to take' means one lot of letters go next to another.
'a look' becomes 'peer' (to peer at something is to look at it).
'around' indicates putting letters inside.
'i'+'on'='ion'
'ion' placed into 'peer' is 'PIONEER'.
'first' acts as a link.
Can you help me to learn more?
(Other definitions for pioneer that I've seen before include "Explorer - innovator" , "Lead the way" , "Innovator; first settler" , "First to explore a new area" , "An explorer in new territory" .)