Good student losing heart, one gathers (7)
I believe the answer is:
gleaner
'one gathers' is the definition.
(I've seen this before)
'good student losing heart' is the wordplay.
'good' becomes 'g' (abbreviation).
'student' becomes 'learner' (I've seen this before).
'losing heart' says to hollow out the word (remove centre letters).
'learner' with its middle taken out is 'leaner'.
'g'+'leaner'='GLEANER'
(Other definitions for gleaner that I've seen before include "Description of Ruth" , "one gathers" , "Person gathering" , "Collector of leftover grain after a harvest" , "Leftover grain gatherer" .)