Each German only half enthusiastic (5)
I believe the answer is:
eager
'enthusiastic' is the definition.
(similar in meaning)
'each german only half' is the wordplay.
'each' becomes 'ea' (abbreviation).
'only half' indicates taking half.
'german' halved is 'ger'.
'ea'+'ger'='EAGER'
(Other definitions for eager that I've seen before include "hungry" , "Earnest" , "Ardent" , "Enthusiastic, raring to go" , "Anxious" .)