Suppose example won't begin to contain problem? (6)
I believe the answer is:
assume
'suppose' is the definition.
(assume can mean to suppose or expect)
'example won't begin to contain problem?' is the wordplay.
'example' becomes 'case' (case can mean an example or instance of something).
'won't begin' means to remove the first letter.
'to contain' is an insertion indicator.
'problem?' becomes 'sum' (arithmetic problem).
'case' with its first letter taken away is 'ase'.
'ase' going around 'sum' is 'ASSUME'.
(Other definitions for assume that I've seen before include "Wrongly take" , "Guess" , "Adopt falsely" , "Take or put on" , "Claim without justification" .)