The demand for telephonic communication? (4)
I believe the answer is:
call
This could be a double definition.
'the demand for' is the first definition.
(thesaurus)
'telephonic communication?' is the second definition.
'call' can be an answer for 'communication?' (call is a kind of communication). I'm not sure about the 'telephonic' bit.
Can you help me to learn more?
(Other definitions for call that I've seen before include "Ireland's ..., rugby anthem" , "Hail; visit" , "Pay a visit" , "Be in control" , "That is enough" .)