Jamming in concert, acquiring name after moving north (9)
I believe the answer is:
thronging
'jamming' is the definition.
('throng' can be a synonym of 'jam')
'concert acquiring name after moving north' is the wordplay.
'concert' becomes 'gig' (I've seen this in another clue).
'acquiring' is an insertion indicator.
'name' becomes 'n' (common abbreviation e.g. on forms).
'after' is a charade indicator (letters next to each other).
'moving' indicates anagramming the letters (letters are moved around).
'gig' enclosing 'n' is 'ging'.
'north' anagrammed gives 'thron'.
'ging' put after 'thron' is 'THRONGING'.
'in' is the link.
(Another definition for thronging that I've seen is " Pressing".)