Pondering briefly to absorb learner's fine material (6)
I believe the answer is:
muslin
'fine material' is the definition.
'pondering briefly to absorb learner's' is the wordplay.
'pondering' becomes 'musing' (synonyms).
'briefly' means to remove the last letter.
'to absorb' means one lot of letters goes inside another.
'learner' becomes 'l'.
'musing' with its last letter removed is 'musin'.
'musin' going around 'l' is 'MUSLIN'.
(Other definitions for muslin that I've seen before include "Lightweight cotton cloth" , "Gauze-like cloth" , "dress material" , "Lightweight cotton fabric" , "Light cotton cloth" .)