Verse by Forster used in a song and a prayer (3,5)
I believe the answer is:
ave maria
'a prayer' is the definition.
(Ave Maria is an example)
'verse by forster used in a song' is the wordplay.
'verse' becomes 'v'.
'by' means one lot of letters go next to another.
'forster' becomes 'em' (I've seen this in other clues).
'used in' indicates putting letters inside.
'song' becomes 'aria' (aria is a kind of song).
'v'+'em'='vem'
'a'+'aria'='aaria'
'vem' going into 'aaria' is 'AVE MARIA'.
'and' is the link.
(Other definitions for ave maria that I've seen before include "Work of Schubert" , "Catholic prayer" , "Hail Mary, in Latin" , "Hail Mary (Lat.)" , "Hail Mary in prayer (3.5)" .)