Left-of-centre sorts often fail to think things over (7)
I believe the answer is:
reflect
'think things over' is the definition.
'reflect' can be an answer for 'think' (reflecting is a kind of thinking). I'm unsure of the 'things over' bit.
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for reflect that I've seen before include "Meditate - mirror - show" , "shed" , "Think or mirror" , "chew the cud" , "Cogitate" .)