Centrist's head in the sand — one never learns (5)
I believe the answer is:
dunce
'one never learns' is the definition.
I can't tell whether this defines the answer.
'centrist's head in the sand' is the wordplay.
'head' indicates taking the first letters.
'in the' is an insertion indicator.
'sand' becomes 'dune' (I can't explain this - if you can you should believe this answer much more).
The first letter of 'centrists' is 'c'.
'c' placed into 'dune' is 'DUNCE'.
Can you help me to learn more?
(Other definitions for dunce that I've seen before include "School fool" , "He never learns" , "One slow to pick" , "Poor learner" , "Blockhead" .)