Boys are first changing causes (7)
I believe the answer is:
reasons
'changing causes' is the definition.
The definition and answer can be both related to communication as well as being plural nouns.
Maybe you can see an association between them that I can't see?
'boys are' is the wordplay.
I cannot quite understand how this works, but
'boys' could be 'sons' ('son' can be a synonym of 'boy') and 'sons' is found within the answer.
an anagram of 'are' is 'rea' which is within the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
'first' acts as a link.
Can you help me to learn more?
(Other definitions for reasons that I've seen before include "excuses" , "Ness oar (anag.)" , "Logically deduces" , "Motives, rounds" , "Motives, explanations" .)