Service just on the radio? (4)
I believe the answer is:
rite
'service' is the definition.
(thesaurus)
'just on the radio?' is the wordplay.
'just' becomes 'right' ('right' can be similar in meaning to 'just').
'on the radio?' shows a homophone (sound like) (I've seen 'on the radio' mean this).
'right' is a homophone of 'RITE'.
(Other definitions for rite that I've seen before include "Ceremony, liturgy" , "(Words used in) ceremonial" , "(Words for) ceremony" , "Tries awkwardly to perform rituals" , "something like mass" .)