Head of the hospital department, Margaret, is a help in securing temporary accommodation (4,3)
I believe the answer is:
tent peg
'a help in securing temporary accommodation' is the definition.
(tents accommodate people temporarily)
'head of the hospital department margaret' is the wordplay.
'head of' indicates taking the first letters.
'hospital department' becomes 'ENT' (abbreviation for Ear, Nose and Throat department).
'margaret' becomes 'Peg' (nickname for someone called Margaret).
The first letter of 'the' is 't'.
't'+'ent'+'peg'='TENT-PEG'
'is' acts as a link.
(Other definitions for tent peg that I've seen before include "It's driven into the ground to support portable shelter" , "Securer for marquee" , "Fixer for guy" , "Fastener for guy" , "will hold a guy down" .)