Bottle essential for life without heart (4)
I believe the answer is:
vial
'bottle' is the definition.
(vial is a kind of bottle)
'essential for life without heart' is the wordplay.
'essential for life' becomes 'vital' (I've seen this before).
'without heart' suggests removing the centre.
'vital' with its middle removed is 'VIAL'.
(Other definitions for vial that I've seen before include "Small container for liquid medicine" , "Small glass container" , "Bottle that contains a drug" , "Small container for liquids" , "Small bottle used for medicines, laboratory work, etc" .)