Small step men exploring this would take (5)
I believe the answer is:
space
'men exploring this would take' is the definition.
The definition suggests a singular noun which matches the answer.
'small step' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'step' becomes 'pace' (pace is a kind of step).
's'+'pace'='SPACE'
Can you help me to learn more?
(Other definitions for space that I've seen before include "Free area" , "Gap between words" , "-- Capsule; -- bar" , "Expanse" , "Blank" .)