Record one's lines for occasion (7)
I believe the answer is:
episode
'for occasion' is the definition.
(thesaurus)
'record one's lines' is the wordplay.
'record' becomes 'EP' (abbreviation for extended play record).
'one's' becomes 'i's' (Roman numeral).
'lines' becomes 'ode' (lines of poetry).
'ep'+'is'+'ode'='EPISODE'
(Other definitions for episode that I've seen before include "Story instalment" , "Bout" , "Instalment; incident" , "Incident or event as part of sequence" , "One part of a series" .)