Do without a hand signal (5)
I believe the answer is:
flare
'signal' is the definition.
(flare is a kind of signal)
'do without a hand' is the wordplay.
'do' becomes 'fare' (synonyms).
'without' means one lot of letters goes inside another ('without' can be similar in meaning to 'outside').
'a hand' becomes 'L' (abbreviation for left, as in the left-hand side).
'fare' going around 'l' is 'FLARE'.
(Other definitions for flare that I've seen before include "Distress signal; burst out angrily" , "Blaze in feral manner" , "Burn with sudden brightness" , "Sudden burst of flame" , "Widen out like a bell" .)