Means to communicate in period without company (8)
I believe the answer is:
intercom
'means to communicate' is the definition.
'in period without company' is the wordplay.
'period' becomes 'term' (term is a kind of period**).
'without' means one lot of letters goes inside another ('without' can be similar in meaning to 'outside').
'company' becomes 'co' (abbreviation).
'term' placed around 'co' is 'tercom'.
'in'+'tercom'='INTERCOM'
(Other definitions for intercom that I've seen before include "Communications device" , "messaging system" , "Two-way communicator" , "System of communication by radio or telephone" , "System of communication often on door" .)