Trial on air is unreliable and totally unreasonable (10)
I believe the answer is:
irrational
'totally unreasonable' is the definition.
'irrational' can be an answer for 'unreasonable' (similar in meaning). I am not certain of the 'totally' bit.
'trial on air is unreliable' is the wordplay.
'is unreliable' indicates an anagram (an unreliable or inaccurate spelling).
'trial'+'on'+'air'='trialonair'
'trialonair' is an anagram of 'IRRATIONAL'.
'and' acts as a link.
Can you help me to learn more?
(Other definitions for irrational that I've seen before include "Unreasonable" , "Illogical" , "Not logical" , "Crazy" , "Kind of numbers" .)