Make fit, as by giving a girl training (5)
I believe the answer is:
adapt
'make fit' is the definition.
('adapt' can be a synonym of 'make fit')
'giving a girl training' is the wordplay.
'giving' says to put letters next to each other.
'a girl' becomes 'ada' (**).
'training' becomes 'pt'.
'ada'+'pt' is 'ADAPT'.
'as by' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for adapt that I've seen before include "Adjust (to new condition)" , "Accommodate" , "Adjust (to new conditions)" , "Adjust to new circumstances" , "Adjust to changed circumstances" .)