Transplant is a lot of effort (5)
I believe the answer is:
graft
'transplant' is the definition.
(I know that transplant can be written as graft)
'lot of effort' is the wordplay.
I cannot really see how this works, but
'lot' could be 'raft' (synonyms) and 'raft' is present in the answer.
A single letter 'g' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
'is a' acts as a link.
Can you help me to learn more?
(Other definitions for graft that I've seen before include "Slip" , "Shoot; hard work" , "Hard work - corrupt profit" , "Hard work; corruption" , "Labour" .)