Absorb contents of building estimate (6)
I believe the answer is:
ingest
'absorb' is the definition.
(I know that absorb can be written as ingest)
'contents of building estimate' is the wordplay.
'contents of' indicates the answer is hidden within the clue.
'INGEST' is hidden within 'building estimate'.
(Other definitions for ingest that I've seen before include "Eat - gin set (anag)" , "take in, eat" , "Swallow -signet (anag)" , "Absorb mentally" , "Consume food" .)