Is it possible he could be heard? Great! (6)
I believe the answer is:
mighty
'great' is the definition.
(thesaurus)
'is it possible he could be heard?' is the wordplay.
I cannot quite see how this works, but
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is located in the answer.
'he' could be 'hy' and 'hy' is found in the leftover letters.
The remaining letters 'mig' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for mighty that I've seen before include "Having great strength" , "Very powerful/strong" , "Arrogant people are often described as high and . . . . . ." , "Powerful - huge" , "Extremely" .)