Little prick's agent gets introductions to Gielgud, Antony Sher and Herbert Tree (7,3)

'herbert tree' is the definition.
'weeping ash' can be an answer for 'tree' (weeping ash is a type of tree). I'm not sure about the 'herbert' bit.

'little prick's agent gets introductions to gielgud antony sher' is the wordplay.
'little' becomes 'wee' (similar in meaning).
'prick's agent' becomes 'pin' (a pin might be responsible for a prick).
'gets' means one lot of letters go next to another.
'introductions to' suggests taking the first letters.
'sher' becomes 'sh' (I can't explain this - if you can you should believe this answer much more).
The initial letters of 'gielgud antony' is 'ga'.
'wee'+'pin'+'ga'+'sh'='WEEPING-ASH'

'and' is the link.