Regularly tied up, shot in the arm of German (8)
I believe the answer is:
teutonic
'german' is the definition.
(synonyms)
'regularly tied up shot in the arm' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'shot in the arm' becomes 'tonic' (both can mean something which stimulates).
'tied'+'up'='tiedup'
The alternate letters of 'tiedup' are 'teu'.
'teu'+'tonic'='TEUTONIC'
'of' acts as a link.
(Other definitions for teutonic that I've seen before include "Of the Germanic peoples" , "German (e.g. thoroughness)" , "Characteristic of Germans" , "Relating to the Germanic language" , "from Germany" .)