Thought Lab team blue? Exactly the opposite (10)
I believe the answer is:
considered
'thought' is the definition.
(considering is a kind of thinking)
'lab team blue? exactly the opposite' is the wordplay.
I cannot quite understand how this works, but
'team' could be 'side' (I've seen this before) and 'side' is found in the answer.
'blue?' could be 'con' (I've seen this in other clues) and 'con' is found within the answer.
The remaining letters 'red' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
(Other definitions for considered that I've seen before include "Thought carefully about" , "Believed to be" , "Looked at" , "respected" , "Deliberated" .)