Heinrich? He gets in with a key (5)
I believe the answer is:
heine
'heinrich? he gets in with a key' is the definition.
The definition suggests a singular noun which matches the answer.
'he gets in with a key' is the wordplay.
'gets' is a charade indicator (letters next to each other).
'with' is a charade indicator (letters next to each other).
'a key' becomes 'E' (a musical key).
'he'+'in'+'e'='HEINE'
Can you help me to learn more?
(Other definitions for heine that I've seen before include "Heinrich -, nineteenth century German poet" , "Heinrich -, Ger. poet" .)