It’s difficult stuff, researching salad ingredient? (6,7)
I believe the answer is:
rocket science
'it's difficult stuff' is the definition.
(rocket science is famously difficult)
'researching salad ingredient?' is the wordplay.
I cannot really see how this works, but
'salad ingredient?' could be 'rocket' (I've seen this before) and 'rocket' is found within the answer.
The remaining letters 'science' 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).
Can you help me to learn more?
(Other definitions for rocket science that I've seen before include "Space technology" , "(Not) an intellectual demand (slang)" , "Scenic eco-trek (anag) -- complex subject for boffins?" , "Proverbial activity requiring greater intelligence?" , "Something said to require great intelligence (usually referred to in the negative)" .)