Aah's partner (3)
I believe the answer is:
ooh
'aah's partner' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ooh that I've seen before include "Exclamation of surprise or pain" , "sound excited" , "My goodness!" , "Exclamation of delight" , "expression of delight" .)