Group line should be held in general (7)
I believe the answer is:
cluster
'group' is the definition.
(cluster is a kind of group)
'line should be held in general' is the wordplay.
'line' becomes 'l'.
'should be held in' indicates putting letters inside.
'general' becomes 'custer' (I've seen this before).
'l' going inside 'custer' is 'CLUSTER'.
(Other definitions for cluster that I've seen before include "Crowded jumble" , "Group or bunch" , "Closely-spaced group" , "Come together" , "Group, clump" .)