Note a series of low points (6)
I believe the answer is:
minima
'low points' is the definition.
(plural of minimum)
'note a' is the wordplay.
'note' becomes 'minim' (type of musical note).
'minim'+'a'='MINIMA'
'series of' acts as a link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for minima that I've seen before include "Lowest values" , "Lowest quantity or amount" , "lowest possible degrees" , "Lowest possible amounts" , "Stevenson's mutable doctor" .)