Being in hand, half of us get extra (6)
I believe the answer is:
spares
'being in hand half of us get extra' is the definition.
I can't judge whether this definition defines the answer.
'being in hand half of us get' is the wordplay.
'being in' becomes 'spas' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'hand' becomes 'R' (abbreviation for right, as in the right-hand side).
'half of' means to take half the letters.
'us' becomes 'we'.
'get' is an insertion indicator.
'we' cut in half is 'e'.
'r'+'e'='re'
'spas' going around 're' is 'SPARES'.
Can you help me to learn more?
(Other definitions for spares that I've seen before include "Is merciful towards, refrains from hurting" , "Extras with spears" , "Lets off; reserve parts" , "Extras in case of necessity" , "Replacement items, like tyres" .)