What a fellow needs a bit of help in building (6)
I believe the answer is:
chapel
'building' is the definition.
(chapel is a kind of building)
'what a fellow needs a bit of help' is the wordplay.
'what a fellow' becomes 'chap' (synonyms).
'needs' means one lot of letters go next to another.
'a bit of help' becomes 'el' (I can't explain this - if you can you should believe this answer much more).
'chap'+'el'='CHAPEL'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for chapel that I've seen before include "Nonconformist building (with a father!)" , "Nonconformist church" , "Place of worship set apart in church or cathedral" , "Place used for Christian worship - smaller than cathedral" , "Union members" .)