Shrink is about to medicate (7)
I believe the answer is:
retreat
'shrink' is the definition.
(thesaurus)
'about to medicate' is the wordplay.
'about' becomes 're' (regarding).
'to medicate' becomes 'treat' (I've seen this before).
're'+'treat'='RETREAT'
'is' is the link.
(Other definitions for retreat that I've seen before include "concession" , "retirement" , "Withdraw from battle" , "Pull back" , "snug" .)