Well-regarded magazine finally joins up with editor (8)
I believe the answer is:
esteemed
'well-regarded' is the definition.
(I've seen this in another clue)
'magazine finally joins up with editor' is the wordplay.
'finally' says to take the final letters.
'joins' becomes 'meets' (meeting is a kind of joining).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'with' says to put letters next to each other.
'editor' becomes 'ed' (abbreviation).
The final letter of 'magazine' is 'e'.
'meets' reversed gives 'steem'.
'e'+'steem'+'ed'='ESTEEMED'
(Other definitions for esteemed that I've seen before include "Respected and valued, like customer" , "Admirable" , "Held in high regard, as customer may be" , "Had great respect for" , "Dear" .)