Sentimental lad largely taking man's place in automatic (7)
I believe the answer is:
robotic
'automatic' is the definition.
(robotic can mean automatic or mechanical)
'sentimental lad largely taking man's place' is the wordplay.
I cannot quite understand how this works, but
'man' could be 'robot' (I have seen 'Mechanical man ' mean 'robot' so perhaps 'man' could also mean 'robot') and 'robot' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
'in' acts as a link.
Can you help me to learn more?
(Other definitions for robotic that I've seen before include "Moving mechanically" , "Automaton-like" , "Like a mechanical man" , "Like the Tin Man" , "Of or using automatons" .)