Composure of salesman taking nothing to the London area (6)
I believe the answer is:
repose
'composure' is the definition.
(repose is a kind of composure)
'salesman taking nothing to the london area' is the wordplay.
'salesman' becomes 'rep' (I've seen this before).
'taking' means one lot of letters go next to another.
'nothing' becomes 'o' (looks like zero - 0).
'to the london area' becomes 'se' (abbreviation for South East).
'rep'+'o'+'se'='REPOSE'
'of' is the link.
(Other definitions for repose that I've seen before include "peace" , "Quiet restfulness" , "Relaxation" , "calm" , "place" .)