Cockney's present wish soon given poetic form (7)
I believe the answer is:
erelong
'soon given poetic form' is the definition.
(poetic word for 'soon')
'cockney's present wish' is the wordplay.
'cockney's present' becomes ''ere' ('here' - both can mean in attendance - said with the 'H' dropped - a cockney accent.).
'wish' becomes 'long' (I've seen this in other clues).
'ere'+'long'='ERELONG'
(Other definitions for erelong that I've seen before include "Soon (arch.)" , "Soon (archaic)" , "Soon (poetic)" , "Soon (poetically)" .)