Joins in an endless singsong, possibly? (5,2)
I believe the answer is:
signs on
'joins' is the definition.
The definition and answer can be both to do with social activities as well as being verbs in their -s form.
Perhaps there's a link between them I don't understand?
'an endless singsong possibly?' is the wordplay.
'an endless' means to remove the last letter.
'possibly?' indicates anagramming the letters (I've seen 'possibly' mean this).
'singsong' with its final letter removed is 'singson'.
'singson' is an anagram of 'SIGNS ON'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for signs on that I've seen before include "Hires" , "Employs" .)