Worry about troops governed by D-notice (5)
I believe the answer is:
dread
'worry about' is the definition.
'troops governed by d-notice' is the wordplay.
'troops' becomes 're' (I've seen this in other clues).
'governed by' indicates putting letters inside (the inserted letters are contained or governed).
'notice' becomes 'ad'.
'd'+'ad'='dad'
're' put into 'dad' is 'DREAD'.
(Other definitions for dread that I've seen before include "alarm" , "Apprehensive fear" , "Disquiet" , "Be scared of" , "Get cold feet" .)