Tension from hearing perhaps about American power (8)
I believe the answer is:
suspense
'tension' is the definition.
(thesaurus)
'hearing perhaps about american power' is the wordplay.
'hearing perhaps' becomes 'sense' (hearing is a kind of sense**).
'about' indicates putting letters inside.
'american' becomes 'us'.
'power' becomes 'p'.
'us'+'p'='usp'
'sense' going around 'usp' is 'SUSPENSE'.
'from' acts as a link.
(Other definitions for suspense that I've seen before include "feature of exciting fiction?" , "State of uncertainty about the future" , "Excitement and uncertainty about an outcome" , "Feeling of excitement or anxiety about what might happen" , "Tense uncertainty" .)