Decorate a pole up north (5)
I believe the answer is:
adorn
'decorate' is the definition.
(synonyms)
'a pole up north' is the wordplay.
'pole' becomes 'rod' (synonyms).
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'north' becomes 'N' (synonyms).
'rod' written backwards gives 'dor'.
'a'+'dor'+'n'='ADORN'
(Other definitions for adorn that I've seen before include "get dressed!" , "Embellish, decorate" , "dress" , "Beautify - decorate - enhance" , "Attire" .)