Strain to make it very clear (6)

I believe the answer is:

stress

I'm a little stuck... Click here to teach me more about this clue!

'strain' is the definition.
(I know that strain can be written as stress)

I don't understand the rest of the clue.

(Other definitions for stress that I've seen before include "Tension - accent" , "'Strain, tension (6)'" , "Emotional tension" , "Strain or accentuate" , "suffering" .)

I've seen this clue in the Evening Standard.

Want a hint initially instead of a full solution? Install my app