Make chap smaller, or double (8)
I believe the answer is:
stuntman
'double' is the definition.
(I've seen this before)
'make chap' is the wordplay.
'make' becomes 'stunt' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'chap' becomes 'man' (I've seen this before).
'stunt'+'man'='STUNTMAN'
'smaller or' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.
(Other definitions for stuntman that I've seen before include "Someone paid to act dangerously" , "Performer of dangerous feats" , "He acts riskily" , "Double for a film's dangerous scenes" , "Performer of dangerous acts in films etc" .)