Period when expecting conclusion from beat poet (9)
I believe the answer is:
trimester
'period when expecting' is the definition.
(period of time when expecting a baby)
'conclusion from beat poet' is the wordplay.
'conclusion from' suggests the final letters.
'poet' becomes 'rimester' (alternative spelling of rhymester).
The final letter of 'beat' is 't'.
't'+'rimester'='TRIMESTER'
(Other definitions for trimester that I've seen before include "Period of three months" , "part of college year" , "American term" , "academic session" , "US academic term" .)