Pace that’s rather ordinary then, initially (4)
I believe the answer is:
trot
'pace' is the definition.
(I've seen this in another clue)
'that's rather ordinary then initially' is the wordplay.
'initially' says to take the initial letters.
The initial letters of 'that rather ordinary then' is 'TROT'.
(Other definitions for trot that I've seen before include "Left-winger - move at a fair speed" , "Go at steady pace" , "A slowish run, perhaps by horse" , "Horse's steady pace" , "leftie" .)