Holding nothing back, putting name forward? Definitely not (4)
I believe the answer is:
nope
'forward? definitely not' is the definition.
I can't judge whether this defines the answer.
'holding nothing back putting name' is the wordplay.
'holding' is an insertion indicator.
'nothing' becomes 'O' (looks like zero - 0).
'back' is a reversal indicator.
'putting' becomes 'ep' (I can't justify this - if you can you should believe this answer much more).
'name' becomes 'n' (common abbreviation e.g. on forms).
'ep'+'n'='epn'
'epn' in reverse letter order is 'npe'.
'o' inserted within 'npe' is 'NOPE'.
Can you help me to learn more?
(Other definitions for nope that I've seen before include "I don't think so!" , "Emphatically not!" , "Not on your life!" , "not with stress" , "You must be joking" .)