Extent of morning section (5)
I believe the answer is:
ambit
'extent' is the definition.
(ambit is a kind of extent)
'morning section' is the wordplay.
'morning' becomes 'am' (as in bi:00 AM).
'section' becomes 'bit' (both can mean part).
'am'+'bit'='AMBIT'
'of' is the link.
(Other definitions for ambit that I've seen before include "round" , "Scope or circuit" , "Scope or confines" , "Circuit, compass" , "Circumference" .)