Held department up showing offer for sale (6)
I believe the answer is:
peddle
'offer for sale' is the definition.
The definition and answer can be both to do with ownership as well as being verbs in their base form.
Perhaps you can see an association between them that I don't see?
'held department up showing' is the wordplay.
'showing' says the answer is hidden in the clue.
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'elddep' is hidden within 'held department'.
'elddep' backwards is 'PEDDLE'.
Can you help me to learn more?
(Other definitions for peddle that I've seen before include "traffic" , "Sell from place to place" , "Deal illegally in (not a lever on a cycle!)" , "Sell (drugs or something hot?)" , "Deal in drugs" .)