Session in Crosby, perhaps ending in Bootle (5)
I believe the answer is:
binge
'session' is the definition.
(eg a drinking session is a binge)
'crosby perhaps ending in bootle' is the wordplay.
'crosby perhaps' becomes 'Bing' (singer Bing Crosby).
'ending in' suggests the final letters.
The last letter of 'bootle' is 'e'.
'bing'+'e'='BINGE'
'in' acts as a link.
(Other definitions for binge that I've seen before include "drunken revelry" , "Bust" , "Bout of excessive activity" , "Bout of indulgence" , "Period of excess" .)