Just terrible heading off (8)

I believe the answer is:

rightful

'just' is the definition.
('rightful' can be similar in meaning to 'just')

'terrible heading off' is the wordplay.
'terrible' becomes 'frightful' (I've seen this before).
'heading off' means to remove the first letter.
'frightful' with its first letter taken off is 'RIGHTFUL'.

(Other definitions for rightful that I've seen before include "Proper - legitimate" , "Legitimate, fitting" , "Legitimate - deserved" , "Legitimately claimed" , "Proper, due" .)

I've seen this clue in The Telegraph.

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