Mind you, lies spread about conservationists in a biased way (13)
I believe the answer is:
tendentiously
'in a biased way' is the definition.
(tendentious means biased or distorted)
'mind you lies spread about conservationists' is the wordplay.
I cannot really see how this works, but
'mind' could be 'tend' (to tend is to look after or mind somebody) and 'tend' is present in the answer.
'you' could be 'u' (commonly used in online communication) and 'u' is found in the answer.
'conservationists' could be 'nt' (abbreviation for National Trust) and 'nt' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Another definition for tendentiously that I've seen is " In a controversially biased manner".)