Engineers and soldier hold the brace for the mechanic (9)
I believe the answer is:
repairman
'the mechanic' is the definition.
(I've seen this before)
'engineers and soldier hold the brace' is the wordplay.
'engineers' becomes 're' (abbreviation for Royal Engineers).
'and' is a charade indicator (letters next to each other).
'soldier' becomes 'man' (I've seen this before).
'hold' means one lot of letters goes inside another.
'the brace' becomes 'pair' (a brace is a pair of something).
're'+'man'='reman'
'reman' enclosing 'pair' is 'REPAIRMAN'.
'for' acts as a link.
(Other definitions for repairman that I've seen before include "An engineer" , "Machinery fixer" , "One who makes machines or appliances work again" , "Mr Fix-it" , "One making good" .)