German god, now retired, receives thanks (5)
I believe the answer is:
wotan
'german god' is the definition.
(god in Germanic mythology)
'now retired receives thanks' is the wordplay.
'retired' says the letters should be written in reverse.
'receives' indicates putting letters inside.
'thanks' becomes 'ta' (UK informal version of 'thank you').
'now' written backwards gives 'won'.
'won' placed around 'ta' is 'WOTAN'.
(Other definitions for wotan that I've seen before include "Germanic god" , "Another name for Odin" , "Wagnerian head god" , "Supreme god" , "Teutonic god in the Ring Cycle" .)