Ever decreasing, it looks a bit eerie (3)
I believe the answer is:
eer
'ever' is the definition.
(synonyms)
'decreasing it looks a bit eerie' is the wordplay.
I cannot really understand how this works, but
'it' could be 'e' ('e' can mean 'electronic' which is similar to 'IT') and 'e' is located in the answer.
The remaining letters 'er' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for eer that I've seen before include "Always (poetical)" , "Ever poetically" , "Ever to the poet (3)." , "Always (poetic)" , "Before, poetically speaking (1'2)" .)