Against fastening on edge, like some earrings? (4-2)
I believe the answer is:
clip-on
'like some earrings?' is the definition.
(I've seen this in another clue)
'against fastening on' is the wordplay.
'against' means one lot of letters go next to another.
'fastening' becomes 'clip' (clip is a kind of fastening).
'clip' next to 'on' is 'CLIP-ON'.
'edge' acts as a link.
I am not very happy about this link. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for clip-on that I've seen before include "Attachable" , "Gripping accessory" , "Easily removable tie" , "Kind or earring or bow tie" , "Attached like a bow tie, for example" .)