Visible embarrassment as second transmitter goes west (7)
I believe the answer is:
redness
'visible embarrassment' is the definition.
'second transmitter goes west' is the wordplay.
'second' becomes 's' (common abbreviation).
'transmitter' becomes 'sender' (synonyms).
'goes west' says the letters should be written backwards.
's'+'sender'='ssender'
'ssender' back-to-front is 'REDNESS'.
'as' is the link.
(Other definitions for redness that I've seen before include "Inflamed appearance" , "Appearance of inflammation" .)