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' suggests taking the first letters.
The first 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" .)