Taut or strained (5)
I believe the answer is:
tense
This clue is a double definition.
'taut' is the first definition.
(similar in meaning)
'strained' is the second definition.
(similar in meaning)
(Other definitions for tense that I've seen before include "Verb form, indicates time" , "not together?" , "Attribute of verbs signalling time" , "Worried" , "On edge" .)