Frantic call about a very upset mother (6,3)
I believe the answer is:
raving mad
'frantic' is the definition.
(thesaurus)
'call about a very upset mother' is the wordplay.
'call' becomes 'ring' ('ring' can be a synonym of 'call').
'about' indicates putting letters inside.
'a very' becomes 'av' (I've seen this in other clues).
'upset mother' becomes 'mad' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'ring' going around 'av' is 'raving'.
'raving'+'mad'='RAVING MAD'
Can you help me to learn more?
(Other definitions for raving mad that I've seen before include "Go stark . . . . . . . . . - completely bonkers" , "Very angry" , "Barking" , "Stark . . . . . . . . . - utterly bonkers" .)