Not at all simple to work out in detail (9)
I believe the answer is:
elaborate
'detail' is the definition.
(I've seen this before)
'not at all simple to work out' is the wordplay.
I cannot really see how this works, but
'not' could be 'o' (I've seen this in other clues) and 'o' is found within the answer.
'at' is within the answer.
'work' could be 'lab' (lab is a kind of work) and 'lab' is present in the answer.
The remaining letters 'ere' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'in' is the link.
Can you help me to learn more?
(Other definitions for elaborate that I've seen before include "With many parts or details, maybe a pattern" , "Present in further detail" , "Add details to clarify meaning" , "Describe in detail, being complicated" , "very busy" .)