Theatre company within month: it’s worn out (8)
I believe the answer is:
decrepit
'worn out' is the definition.
(I've seen this before)
'theatre company within month it's' is the wordplay.
'theatre company' becomes 'rep' (short for 'repertory theatre').
'within' means one lot of letters goes inside another.
'month' becomes 'dec' (Dec is an example).
'it's' becomes 'it' (I've seen this in other clues).
'dec'+'it'='decit'
'rep' inserted within 'decit' is 'DECREPIT'.
(Other definitions for decrepit that I've seen before include "past its best" , "Old and feeble" , "Impaired by age" , "Elderly, infirm" , "Getting on" .)