Not be serious about woman as PA (6)
I believe the answer is:
tannoy
'pa' is the definition.
(a public address system)
'not be serious about woman' is the wordplay.
'not be serious' becomes 'toy' (to toy is to play or be unserious).
'about' is an insertion indicator.
'woman' becomes 'Ann' (woman's name).
'toy' placed around 'ann' is 'TANNOY'.
'as' is the link.
(Other definitions for tannoy that I've seen before include "Speaker" , "Orator's amplifier" , "Loudspeaker system" , "Sound amplification system" , "Public address system" .)