A couple of things in common (3)
I believe the answer is:
ems
'a couple of things in common' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ems that I've seen before include "Printers' measures" , "spaces at the printing house" , "Printer's units, each two ens" , "Measurement units in printing" , "Units used in printing" .)