Consider that the experimenter tainted ingredients inside (9)
I believe the answer is:
entertain
'consider' is the definition.
(I know that entertain is a more specific form of the action contemplate)
'the experimenter tainted ingredients inside' is the wordplay.
'inside' says the answer is hidden in the clue.
'ENTERTAIN' is hidden in the letters of 'experimenter tainted ingredients'.
'that' is the link.
(Other definitions for entertain that I've seen before include "Have company" , "Put up" , "Provide amusement" , "Act as host" , "Play host to" .)