A long pace with one leg each side (7)
I believe the answer is:
astride
'with one leg each side' is the definition.
(eg being astride a horse)
'a long pace' is the wordplay.
'long pace' becomes 'stride' (I've seen this before).
'a'+'stride'='ASTRIDE'
(Other definitions for astride that I've seen before include "Not side saddle" , "With a leg on both sides" , "With legs stretched apart - tirades (anag)" , "It dares to be with legs wider apart" , "With one leg on either side, as sitting on horse" .)