Time and pounds invested in more unusual child (7)
I believe the answer is:
toddler
'child' is the definition.
(toddler is a kind of child)
'time and pounds invested in more unusual' is the wordplay.
'time' becomes 't'.
'and' means one lot of letters go next to another.
'pounds' becomes 'l' (L can represent the monetary pound).
'invested in' means one lot of letters goes inside another.
'more unusual' becomes 'odder' ('odd' can be similar in meaning to 'unusual').
'l' inserted within 'odder' is 'oddler'.
't'+'oddler'='TODDLER'
(Other definitions for toddler that I've seen before include "Feeble walker" , "youngster" , "Little one" , "Infant" , "Child starting to walk" .)