Staff party set up to follow conclusion of seminar (3)
I believe the answer is:
rod
'staff' is the definition.
(both can mean a pole or stick)
'set up to follow conclusion of seminar' is the wordplay.
'set' becomes 'do' (synonyms).
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'to follow' means one lot of letters go next to another (some letters go after or follow others).
'conclusion of' indicates one should take the final letters.
The last letter of 'seminar' is 'r'.
'do' reversed gives 'od'.
'od' after 'r' is 'ROD'.
'party' acts as a link.
(Other definitions for rod that I've seen before include "Thin straight bar" , "A few yards" , "Long, straight stick" , "The fly fisherman's stick" , "Baton, pole" .)