Iago’s end almost excited worry (7)
I believe the answer is:
agonise
'worry' is the definition.
(I've seen this before)
'iago's end almost excited' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'excited' indicates anagramming the letters.
'iagos'+'end'='iagosend'
'iagosend' with its final letter removed is 'iagosen'.
'iagosen' with letters rearranged gives 'AGONISE'.
(Other definitions for agonise that I've seen before include "Worry intensely" , "Fret, worry inordinately" , "Suffer torment" , "Struggle mentally" , "Be very worried" .)