With no hesitation saintly and not heartless in trouble (9)
I believe the answer is:
instantly
'with no hesitation saintly and not heartless in trouble' is the definition.
I can't judge whether this definition defines the answer.
'saintly and not heartless in trouble' is the wordplay.
'and' says to put letters next to each other (I've seen this in other clues).
'heartless' means to remove the middle letters.
'in trouble' is an anagram indicator.
'not' with its centre removed is 'nt'.
'saintly' put after 'nt' is 'ntsaintly'.
'ntsaintly' with letters rearranged gives 'INSTANTLY'.
Can you help me to learn more?
(Other definitions for instantly that I've seen before include "Immediately, forthwith" , "Without delay or hesitation" , "With no delay, this very second" .)