Group, engineers, points to decay (8)
I believe the answer is:
gangrene
'decay' is the definition.
(thesaurus)
'group engineers points' is the wordplay.
'group' becomes 'gang' (a gang is a group of people).
'engineers' becomes 're' (abbreviation for Royal Engineers).
'points' becomes 'ne' (North and East).
'gang'+'re'+'ne'='GANGRENE'
'to' is the link.
(Other definitions for gangrene that I've seen before include "Decay of body tissue from lack of blood" , "Local death of body tissue" , "Tissue decay from interrupted blood supply" , "Pathological condition" , "Decay of body tissue for want of blood supply" .)