Mention location on the phone? (4)
I believe the answer is:
cite
'mention' is the definition.
(synonyms)
'location on the phone?' is the wordplay.
'location' becomes 'site' (site is a kind of location).
'on the phone?' indicates a 'sounds like' (homophone) clue (I've seen 'on the phone' mean this).
'site' is a homophone of 'CITE'.
(Other definitions for cite that I've seen before include "Summon - quote" , "Quote as evidence" , "Repeat a passage from some written work" , "Adduce as proof" , "Quote as authority" .)