Sentry head of logistics treated harshly (7)
I believe the answer is:
sternly
'harshly' is the definition.
(thesaurus)
'sentry head of logistics treated' is the wordplay.
'head of' suggests taking the first letters.
'treated' indicates an anagram.
The initial letter of 'logistics' is 'l'.
'sentry'+'l'='sentryl'
'sentryl' with letters rearranged gives 'STERNLY'.
(Other definitions for sternly that I've seen before include "In serious way" , "Cruelly" .)