Plant that means a great deal to us (5)
I believe the answer is:
lotus
'plant that' is the definition.
'lotus' can be an answer for 'plant' (lotus is a flowering plant). I'm not sure about the remainder of the definition.
'a great deal to us' is the wordplay.
'a great deal' becomes 'lot' (both can mean a large amount).
'lot'+'us'='LOTUS'
'means' is the link.
Can you help me to learn more?
(Other definitions for lotus that I've seen before include "Water-lily; yoga position" , "Large water lily" , "Indian waterlily" , "Aquatic plant" , "In Greek mythology, a fruit which induces forgetfulness" .)