Jittery Tory leader seen out (5)
I believe the answer is:
tense
'jittery' is the definition.
(similar in meaning)
'tory leader seen out' is the wordplay.
'leader' suggests taking the first letters.
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
The first letter of 'tory' is 't'.
'seen' with letters rearranged gives 'ense'.
't'+'ense'='TENSE'
(Other definitions for tense that I've seen before include "perfect, perhaps" , "imperfect, perhaps?" , "Maybe future" , "quite possibly perfect" , "past possibly" .)