Supposed it was the piano one had taken up again (8)
I believe the answer is:
presumed
'supposed' is the definition.
(I've seen this before)
'piano one had taken up again' is the wordplay.
'piano' becomes 'p' (musical abbreviation).
'one had' becomes 'd' (in contractions e.g. 'I'd', 'you'd' etc).
'taken' is an insertion indicator.
'up again' becomes 'resume' (I can't justify this - if you can you should believe this answer much more).
'p'+'d'='pd'
'pd' placed around 'resume' is 'PRESUMED'.
'it was the' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for presumed that I've seen before include "thought" , "expected" , "Took for granted" , "Was impertinent" , "Supposed" .)