Measure them casually - it's symbolic (5)
I believe the answer is:
totem
'casually it's symbolic' is the definition.
I can't tell whether this definition defines the answer.
'measure them' is the wordplay.
'measure' becomes 'tot' (I have seen 'Measure of spirits' mean 'tot' so perhaps 'measure' could also mean 'tot').
'them' becomes 'em' (abbreviation).
'tot'+'em'='TOTEM'
Can you help me to learn more?
(Other definitions for totem that I've seen before include "symbol representing clan" , "Spiritually significant emblem" , "Sort of pole" , "This pole is carved and painted by N American Indians" , "something sacred" .)