Those people absorbing an alternative abstract idea (6)
I believe the answer is:
theory
'abstract idea' is the definition.
'theory' can be an answer for 'idea' (theory is a kind of idea). I'm not certain of the 'abstract' bit.
'those people absorbing an alternative' is the wordplay.
'those people' becomes 'they' ('they' refers to a group of people).
'absorbing' indicates putting letters inside.
'an alternative' becomes 'or'.
'they' placed around 'or' is 'THEORY'.
Can you help me to learn more?
(Other definitions for theory that I've seen before include "Ideal situation" , "Proposed explanation of something" , "Working hypothesis" , "Supposition intended to explain observations" , "The words, as opposed to the practice" .)