Mother to rant about secret word (6)
I believe the answer is:
mantra
'secret word' is the definition.
'mantra' can be an answer for 'word' (I have seen 'Sacred word ' mean 'mantra' so perhaps 'word' could also mean 'mantra'). I am unsure of the 'secret' bit.
'mother to rant about' is the wordplay.
'mother' becomes 'ma' (ma can mean mother).
'about' indicates an anagram.
'rant' anagrammed gives 'ntra'.
'ma'+'ntra'='MANTRA'
Can you help me to learn more?
(Other definitions for mantra that I've seen before include "Much-repeated phrase" , "Buddhist chant" , "Sacred text used as incantation" , "repeating phrase" , "Sound repeated as an aid to meditation" .)