Encouraging shot -- golfer isn't losing length (9)
I believe the answer is:
'encouraging' is the definition.
(fostering is a kind of encouraging)
'shot golfer isn't losing length' is the wordplay.
'shot' is an anagram indicator.
'losing' suggests deleting specific letters.
'length' becomes 'l' (abbreviation in geometry).
'golferisnt' with 'l' removed is 'goferisnt'.
'goferisnt' is an anagram of 'FOSTERING'.
(Another definition for fostering that I've seen is " Looking after".)