Gather Jenny maybe is nursing old lady (5)
I believe the answer is:
amass
'gather' is the definition.
(synonyms)
'jenny maybe is nursing old lady' is the wordplay.
'jenny maybe' becomes 'ass' (jenny is a female ass).
'is nursing' means one lot of letters goes inside another.
'old lady' becomes 'ma'.
'ass' going around 'ma' is 'AMASS'.
(Other definitions for amass that I've seen before include "Build up" , "Accumulate over time" , "Put together" , "Collect, hoard" , "Accrue, heap up" .)