Small group of working mothers network operator blocks (9)

I believe the answer is:
threesome
'small group' is the definition.
(I've seen this before)
'working mothers network operator blocks' is the wordplay.
I cannot really see how this works, but
'network' could be 'ee' (British mobile network EE) and 'ee' is found in the answer.
an anagram of 'mothers' is 'thrsome' which is present in the left over letters.
This accounts for all the letters.
This explanation may well be incorrect...
'of' acts as a link.
Can you help me to learn more?
(Other definitions for threesome that I've seen before include "Small group of people" , "One more than a couple" , "Freeman Hardy Willis, say" , "The Fates, perhaps" , "Those wise men could be" .)
