Agricultural study of one of those in the cabbage family - in a funny way, it's not complicated (6,7)

I believe the answer is:

rocket science

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(Other definitions for rocket science that I've seen before include "Proverbial activity requiring greater intelligence?" , "(Not) an intellectual demand (slang)" , "Something very difficult to understand (involving gravity?)" , "Space technology" , "Great technical skill" .)

I've seen this clue in the Irish Times and the Irish Times (Crosaire).

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