Astronomer has front of telescope crushed by rod — gosh! (7)
I believe the answer is:
ptolemy
'astronomer' is the definition.
(Ptolemy is an example)
'front of telescope crushed by rod gosh' is the wordplay.
'front of' indicates taking the first letters.
'crushed by' means one lot of letters goes inside another.
'rod' becomes 'pole' (pole is a kind of rod).
'gosh' becomes 'my' (both are old-fashioned expressions of surprise).
The initial letter of 'telescope' is 't'.
't' inserted into 'pole' is 'ptole'.
'ptole'+'my'='PTOLEMY'
'has' is the link.
(Other definitions for ptolemy that I've seen before include "Egyptian king or astronomer" , "Alexandrian astronomer" , "Ancient astronomer" , "Greek astronomer; Greco-Egyptian ruler" , "Egyptian ruler; Greek astronomer" .)