Tense mistake creating fear (6)
I believe the answer is:
terror
'fear' is the definition.
(I know that terror is a type of fear)
'tense mistake' is the wordplay.
'tense' becomes 't' (abbreviation used in many dictionaries).
'mistake' becomes 'error' (synonyms).
't'+'error'='TERROR'
'creating' is the link.
(Other definitions for terror that I've seen before include "Fear - now being warred on" , "Paralysing fear" , "rogue" , "Abject fear" , "Troublesome child" .)