Absorbent cloth wrapping builder's last tool (6)
I believe the answer is:
trowel
'tool' is the definition.
(trowel is a kind of tool)
'absorbent cloth wrapping builder's last' is the wordplay.
'absorbent cloth' becomes 'towel' (I've seen this before).
'wrapping' means one lot of letters goes inside another.
'last' says to take the final letters.
The final letter of 'builder' is 'r'.
'towel' enclosing 'r' is 'TROWEL'.
(Other definitions for trowel that I've seen before include "Hand tool for plasterers or gardeners" , "One spreads" , "Brickie holds it" , "Bricklayer's tool" , "Beaten egg dish" .)