Large spruces set around, causing feelings of doubt (8)
I believe the answer is:
scruples
'feelings of doubt' is the definition.
'scruples' can be an answer for 'feelings' (scruple is a kind of feeling). I'm unsure of the 'of doubt' bit.
'large spruces set around' is the wordplay.
'large' becomes 'L' (eg in clothes sizes).
'set' indicates anagramming the letters (instruction to set the letters).
'around' indicates putting letters inside.
'spruces' is an anagram of 'scrupes'.
'l' placed inside 'scrupes' is 'SCRUPLES'.
'causing' is the link.
Can you help me to learn more?
(Other definitions for scruples that I've seen before include "Doubts about the morality of an action" , "Qualms" , "Feelings of doubt produced by conscience" , "Doubts stemming from conscience or principles" , "Doubts or hesitations promted by conscience" .)