Set off with small deposit (5)
I believe the answer is:
spark
'set off' is the definition.
(synonyms)
'small deposit' is the wordplay.
I cannot quite see how this works, but
'small' could be 's' (abbreviation - e.g. clothes size) and 's' is present in the answer.
The remaining letters 'park' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'with' is the link.
Can you help me to learn more?
(Other definitions for spark that I've seen before include "Means of ignition" , "Fragment of a burning substance" , "Flicker -- provoke" , "Small electric flash" , "Particle of fire" .)