Lastly, scientist reviews genetic material at animal's den, but there's a flaw in the way experiment is conducted, perhaps (5,3,5)
I believe the answer is:
trial and error
'lastly scientist reviews genetic material at animal's den but there's a flaw in' is the definition.
I can't tell whether this defines the answer.
'way experiment is conducted perhaps' is the wordplay.
I cannot quite understand how this works, but
'way' could be 'error' (I have seen 'Way of operating ' mean 'error' so perhaps 'way' could also mean 'error') and 'error' is present in the answer.
'experiment' could be 'trial' (trial is a kind of experiment) and 'trial' is present in the answer.
The remaining letters 'and' 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).
'the' is the link.
Can you help me to learn more?
(Other definitions for trial and error that I've seen before include "Empirical route to solution" , "Uncertain proceeding" , "Experiment" , "Problem solving by experience" , "Heuristic process" .)