One’s not moved border up (3)
I believe the answer is:
meh
'one's not moved' is the definition.
(both would let a speaker express indifference)
'border up' is the wordplay.
'border' becomes 'hem' (I've seen this before).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'hem' reversed gives 'MEH'.
(Other definitions for meh that I've seen before include "Unexciting (modern slang)" , "Who cares" , "Not much cop" , "am I bovvered?" , "expression of indifference" .)