They can also be played back (5)
I believe the answer is:
'they' is the definition.
Both the definition and answer are plural nouns.
Maybe there's a link between them I don't understand?
'also be played back' is the wordplay.
'also' becomes 'so' (synonyms).
'be played back' becomes 'los' (I can't justify this - if you can you should believe this answer much more).
'so'+'los'='SOLOS'
'can' is the link.
Can you help me to learn more?
(Other definitions for solos that I've seen before include "Musical passages for one instrument" , "Pieces of music for one voice or instrument" , "Unaccompanied parts" , "Passages for one player" , "Numbers" .)