A carer with firm fruit (5)
I believe the answer is:
acorn
'fruit' is the definition.
(acorn is a kind of fruit)
'a carer with firm' is the wordplay.
'carer' becomes 'rn' (I can't justify this - if you can you should believe this answer much more).
'with' is a charade indicator (letters next to each other).
'firm' becomes 'co' (a firm is a company).
'rn' after 'co' is 'corn'.
'a'+'corn'='ACORN'
Can you help me to learn more?
(Other definitions for acorn that I've seen before include "form of seeding" , "oak's fruit" , "Fruit of the oak tree" , "From which a "tall oak" may grow" , "Might source" .)