People who study biology GCSE toil so terribly (10)

I believe the answer is:

ecologists

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

'people who study biology' is the definition.
'ecologists' can be an answer for 'people' (ecologist is a kind of person). I'm not sure about the remainder of the definition.

'gcse toil so terribly' is the wordplay.
'terribly' indicates an anagram.
'gcse'+'toil'+'so'='gcsetoilso'
'gcsetoilso' is an anagram of 'ECOLOGISTS'.

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I've seen this clue in The Times.

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