That male character will follow infant very closely (2,3,6)
I believe the answer is:
to the letter
'very closely' is the definition.
I can't judge whether this defines the answer.
'that male character will follow infant' is the wordplay.
'that male' becomes 'he' (he refers to a man).
'character' becomes 'letter' (letter is a kind of character).
'will follow' says to put letters next to each other.
'infant' becomes 'tot' (tot means a young child).
'he'+'letter'='heletter'
'heletter' after 'tot' is 'TO THE LETTER'.
Can you help me to learn more?
(Other definitions for to the letter that I've seen before include "E.g. contract rigidly so enforced" , "Rent delivered here" , "Where one applies to rent property" , "Where rents go" , "how should tenant's rent be paid?" .)