Friend follows child without reservation (7)
I believe the answer is:
totally
'without reservation' is the definition.
(I've seen this before)
'friend follows child' is the wordplay.
'friend' becomes 'ally' (an ally is a friend or supporter).
'follows' is a charade indicator (letters next to each other).
'child' becomes 'tot' (term for a young child).
'ally' put after 'tot' is 'TOTALLY'.
(Other definitions for totally that I've seen before include "Absolutely" , "Wholly" , "Altogether" , "Utterly" , "Clean" .)