Some crumble, perhaps and tense up (8)
I believe the answer is:
desserts
'some crumble perhaps' is the definition.
I can't judge whether this definition defines the answer.
'tense up' is the wordplay.
'tense' becomes 'stressed' (I've seen this before).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'stressed' back-to-front is 'DESSERTS'.
'and' is the link.
Can you help me to learn more?
(Other definitions for desserts that I've seen before include "Puddings" , "Sweets" , "fools, perhaps?" , "That may be cobblers" , "Last courses" .)