Extent of small stride (5)
I believe the answer is:
space
'extent' is the definition.
(I know that space is a type of area)
'small stride' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'stride' becomes 'pace' (synonyms).
's'+'pace'='SPACE'
'of' acts as a link.
(Other definitions for space that I've seen before include ""The final frontier"" , "Cosmos" , "Interstellar vacuum" , "Empty area, may be outer" , "Gap; --- Oddity (Bowie)" .)