Fluctuating ADC reading for 4-20mA pressure transducer input
A variation of 10 counts out of a maximum 1023 is about 1% of full scale, not bad for an Arduino. This is equivalent to about 50 mV and you probably have that much noise on the input signal and AREF.

If the problem is noise and the noise is a random fluctuation then you should be able to improve the readings by averaging. Try summing 16 or 32 values and then dividing the result by 16 or 32. (I proposed 16 and 32 because they are integer powers of 2 so performing unsigned integer division with these values is easy and fast...shifting.)