Booming boy following engineers with a book (8)
I believe the answer is:
resonant
'booming' is the definition.
(as in a booming sound)
'following engineers with a book' is the wordplay.
'following engineers' becomes 'reso' (I am not sure about this - if you are sure you should believe this answer much more).
'with' means one lot of letters goes inside another.
'a' becomes 'an'.
'book' becomes 'NT' (New Testament).
'an' going inside 'nt' is 'nant'.
'reso'+'nant'='RESONANT'
'boy' is the link.
Can you help me to learn more?
(Other definitions for resonant that I've seen before include "Not saner (anag) - ringing" , "Tending to reinforce sounds" , "Tending to prolong sound, echoing" , "Like" , "Continuing to sound clearly and deeply" .)