Strained future maybe (5)
I believe the answer is:
tense
'strained' is the definition.
(similar in meaning)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for tense that I've seen before include "edgy" , "Stressful" , "Strained by time in grammar" , "In a nervous state" , "Not relaxed" .)