Warning of danger from a member holding line (5)
I believe the answer is:
alarm
'warning of danger' is the definition.
(an alarm alerts you to danger)
'a member holding line' is the wordplay.
'member' becomes 'arm' (member can mean a limb).
'holding' indicates putting letters inside.
'line' becomes 'l' (used when specifying particular lines from a poem).
'a'+'arm'='aarm'
'aarm' placed around 'l' is 'ALARM'.
'from' is the link.
(Other definitions for alarm that I've seen before include "Safety bell or alert signal" , "Announcement of danger" , "Frighten, warning" , "Warning siren" , "Shock; danger signal" .)