A drug designed to support retired conservative members of group (3,5)
I believe the answer is:
old guard
'conservative members of group' is the definition.
(term for the older members of a group)
'a drug designed to support retired' is the wordplay.
'designed' is an anagram indicator (designed with the letters).
'to support' means one lot of letters go next to another (in a down clue, some letters hold others up).
'retired' becomes 'old' (similar in meaning).
'a'+'drug'='adrug'
'adrug' is an anagram of 'guard'.
'guard' put after 'old' is 'OLD GUARD'.
(Other definitions for old guard that I've seen before include "Traditionalists" , "Dinosaurs" , "Long-standing group members, set in their ways" , "who may recall what railways used to be like" , "Long-standing members resistant to change" .)