Power of small river bordering Grand Hotel (8)
I believe the answer is:
strength
'power' is the definition.
(strength is a kind of power)
'small river bordering grand hotel' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'river' becomes 'trent' (I've seen this before**).
'bordering' is an insertion indicator.
'grand' becomes 'g' ('G' can be a synonym of 'grand').
'hotel' becomes 'h' (phonetic alphabet: alpha, bravo, charlie etc.).
'trent' enclosing 'g' is 'trengt'.
's'+'trengt'+'h'='STRENGTH'
'of' acts as a link.
(Other definitions for strength that I've seen before include "Physical energy" , "The longest one-syllable word in English - might" , "Good attribute" , "A good quality; might" , "Concentration" .)