Tension so high always in loud playing field (5,5)
I believe the answer is:
fever pitch
'tension so high' is the definition.
I can't tell whether this definition defines the answer.
'always in loud playing field' is the wordplay.
'always' becomes 'ever' (synonyms).
'in' is an insertion indicator.
'loud' becomes 'f' (short for forte - 'loud' in music).
'playing field' becomes 'pitch' (eg a football pitch).
'f'+'pitch'='fpitch'
'ever' put into 'fpitch' is 'FEVER PITCH'.
Can you help me to learn more?
(Other definitions for fever pitch that I've seen before include "State of intense excitement - fetch viper (anag)" , "Height of excitement" , "State of high excitement" , "in state of great agitation" , "Tremendous excitement" .)