In name, at least, it’s essential (5)
I believe the answer is:
vital
'essential' is the definition.
(similar in meaning)
'in name at least it's' is the wordplay.
'in' indicates putting letters inside.
'name at least' becomes 'val' (I can't justify this - if you can you should give a lot more credence to this answer).
'it's' becomes 'it' (I've seen this in other clues).
'val' placed around 'it' is 'VITAL'.
Can you help me to learn more?
(Other definitions for vital that I've seen before include "Essential, life-giving" , "Are such statistics" , "Spirited" , "Of the greatest importance" , "Essential to life, indispensable" .)