$ cat dd |sed 's/^Cluster//'|sort -k1 -n|sed 's/^\([0-9]\+\)/Cluster\1/'| cut -c 1-20
Cluster5        SP_1003(con
Cluster5        SP_1003(con
Cluster5        SP_1003(con
Cluster6        SP_0917(pil
Cluster6        SP_0917(pil
Cluster6        SP_0917(pil
Cluster7                spr_1379(A
Cluster7                spr_1379(A
Cluster7                spr_1379(A
Cluster8                spr_0324(T
Cluster8                spr_0324(T
Cluster8                spr_0324(T
Cluster9        SP_0733(hyp
Cluster9        SP_0733(hyp
Cluster9        SP_0733(hyp
Cluster10       SP_0042(co
Cluster10       SP_0042(co
Cluster10       SP_0042(co