Crossword Genius

Choose to pen article on start of Rachel Riley’s work, say (2,3)

Ross

I believe the answer is:

op art

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'riley's work say' is the definition.
I can't tell whether this defines the answer.

'choose to pen article on start of rachel' is the wordplay.
'choose' becomes 'opt' (both can mean to pick something).
'to pen' indicates putting letters inside.
'article' becomes 'a' (the indefinite article in English).
'on' means one lot of letters go next to another.
'start of' indicates taking the first letters.
The first letter of 'rachel' is 'r'.
'a'+'r'='ar'
'opt' placed around 'ar' is 'OP-ART'.

Can you help me to learn more?

(Other definitions for op art that I've seen before include "Illusory genre" , "modern movement" , "Modern style" , "Nineteen sixties illusory painting style" , "modern paintings" .)

I've seen this clue in The Guardian.
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