DNA of hard-wearing casual trousers, say? (5)
I believe the answer is:
genes
'dna of hard-wearing casual' is the definition.
I can't judge whether this defines the answer.
'trousers say?' is the wordplay.
'trousers' becomes 'jeans' (denim trousers).
'say?' shows a homophone (sound like) (I've seen 'says' mean this).
'jeans' is a homophone of 'GENES'.
Can you help me to learn more?
(Other definitions for genes that I've seen before include "Biological factors controlling heredity" , "Units of heredity" , "Factors governing heredity, carried by chromosome" , "Units of DNA" .)