Two-sided poster's absorbing at times (9)
I believe the answer is:
bilateral
'two-sided' is the definition.
(synonyms)
'poster's absorbing at times' is the wordplay.
'poster' becomes 'bill' (synonyms).
'absorbing' is an insertion indicator.
'times' becomes 'era' (I am not sure about this - if you are sure you should believe this answer much more).
'at'+'era'='atera'
'bill' enclosing 'atera' is 'BILATERAL'.
Can you help me to learn more?
(Other definitions for bilateral that I've seen before include "Two-sided" , "involving two sides" , "involving more than one party?" , "Involving two parties" , "Undertaken by two parties" .)