Ostensibly where to put a clock's hands (2,3,4,2,2)

I believe the answer is:
on the face of it
'ostensibly' is the definition.
(synonyms)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for on the face of it that I've seen before include "From appearances alone" , "Apparently (2,3,4,2,2)" , "where are the chronometer's hands?" , "you can find a clock's numbers here" , "as it would appear" .)
