The initial hard run in grand opening is exciting (9)
I believe the answer is:
thrilling
'is exciting' is the definition.
(similar in meaning)
'the initial hard run in grand opening' is the wordplay.
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
'initial' suggests taking the first letters.
'run' becomes 'rill' (synonyms).
'opening' says to take the initial letters.
The first letter of 'hard' is 'h'.
The first letter of 'grand' is 'g'.
't'+'h'+'rill'+'in'+'g'='THRILLING'
(Other definitions for thrilling that I've seen before include "Hair-raising" , "Causing pleasurable excitement" , "Extremely exciting" , "Gripping" , "Engrossing" .)