Beginning to include parking rate (5)
I believe the answer is:
speed
'rate' is the definition.
(speed is a kind of rate)
'beginning to include parking' is the wordplay.
'beginning' becomes 'seed' (seed is a kind of beginning).
'to include' is an insertion indicator.
'parking' becomes 'p'.
'seed' enclosing 'p' is 'SPEED'.
(Other definitions for speed that I've seen before include "Rate of progress" , "Expedition" , "Alacrity" , "Rate of travel" , "The going rate" .)