It shows some pressure or bias developing (6)
I believe the answer is:
isobar
'it shows some pressure' is the definition.
The definition suggests a singular noun which matches the answer.
'or bias developing' is the wordplay.
'developing' is an anagram indicator (letters developed into a new form).
'or'+'bias'='orbias'
'orbias' with letters rearranged gives 'ISOBAR'.
Can you help me to learn more?
(Other definitions for isobar that I've seen before include "Line joining places of equal barometric pressure" , "(Map) line of constant atmospheric pressure" , "Evidence of pressure" , "Line of equal barometric pressure on a map" , "Line on map showing barometric pressure" .)