A political label, in short, can be deceptive (4)
I believe the answer is:
cons
'a political label in short can be deceptive' is the definition.
I can't tell whether this defines the answer.
'short can be deceptive' is the wordplay.
'short' suggests taking the first letters.
'be deceptive' becomes 'ons' (I can't explain this - if you can you should believe this answer much more).
The initial letter of 'can' is 'c'.
'c'+'ons'='CONS'
Can you help me to learn more?
(Other definitions for cons that I've seen before include "Tricks" , "Swindles" , "Arguments against" .)