Release earl with German (4)
I believe the answer is:
emit
'release' is the definition.
(to emit is to release or let out)
'earl with german' is the wordplay.
'earl' becomes 'e'.
'with german' becomes 'mit' ('with' in German).
'e'+'mit'='EMIT'
(Other definitions for emit that I've seen before include "'Give off, odour say (4)'" , "Issue" , "Broadcast" , "'Give out, light say (4)'" , "Discharge - utter" .)