German rock singer teaching the French one (7)
I believe the answer is:
lorelei
'german rock singer' is the definition.
(rock in Germany which makes an echoing noise)
'teaching the french one' is the wordplay.
'teaching' becomes 'lore' (I've seen this in other clues).
'the french' becomes 'le' ('the' in French).
'one' becomes 'i' (Roman numeral).
'lore'+'le'+'i'='LORELEI'
(Other definitions for lorelei that I've seen before include "Fatal nymph of the Rhine" , "Legendary German rock singer" , "Legendary siren and rock in the R Rhine" , "Rock-dwelling siren" , "Rhine Rock where siren lived" .)