A little kitten seemed nervous (5)
I believe the answer is:
tense
'nervous' is the definition.
(similar in meaning)
'a little kitten seemed' is the wordplay.
'a little' says the answer is hidden in the clue.
'TENSE' can be found hidden inside 'kitten seemed'.
(Other definitions for tense that I've seen before include "Could be present" , "Future perfect? Could be" , "Nervous or tight" , "imperfect, perhaps?" , "Maybe future" .)