Joins up in order to sing some songs? (5,2)
I believe the answer is:
signs on
'joins up' is the definition.
(I've seen this in another clue)
'in order to sing some songs?' is the wordplay.
'in order' indicates anagramming the letters (the letters in a new order).
'some songs?' becomes 'son' (I can't justify this - if you can you should give a lot more credence to this answer).
'sing' is an anagram of 'sign'.
'sign'+'son'='SIGNS ON'
Can you help me to learn more?
(Other definitions for signs on that I've seen before include "Hires" , "Employs" .)