Silly rot - a man about to become a mother (6)
I believe the answer is:
matron
'to become a mother' is the definition.
I can't tell whether this definition defines the answer.
'silly rot a man' is the wordplay.
'silly' indicates anagramming the letters.
'rot'+'man'='rotman'
'rotman' anagrammed gives 'MATRON'.
'about' acts as a link.
Can you help me to learn more?
(Other definitions for matron that I've seen before include "Former title of today's Senior Nursing Officer" , "Senior nursing officer of old" , "Medical supervisor" , "Head of nursing" , "Middle-aged or elderly married woman" .)