It may be perfect (5)
I believe the answer is:
tense
'it may be perfect' is the definition.
(I've seen this before)
'it may be' is the wordplay.
'it' becomes ''t' (abbreviation. e.g. in 'tis).
'may be' becomes 'ense' (I can't explain this - if you can you should give a lot more credence to this answer).
't'+'ense'='TENSE'
Can you help me to learn more?
(Other definitions for tense that I've seen before include "Anxious, high-strung" , "Future, possibly" , "Future perfect? Could be" , "under stress?" , "Could be present" .)