This paper explores the issues of energy harvesting (EH) and multiple eavesdropping in an underlay cognitive radio network (CRN) that comprises of a secondary transmitter ( $SU_{\mathcal {T}}$ ) and destination ( $SU_{\mathcal {D}}$ ) node connected through a decode-forward (DF) relay ( $S_{\mathcal {R}}$ ). CRN is operated following a frame structure that includes three non-overlapping slots where in the first one, the relay harvests energy from the information signal of $SU_{\mathcal {T}}$ and the interference signal of primary user (PU). During the second slot, $SU_{\mathcal {T}}$ transmits data to the relay node. In the last slot, $S_{\mathcal {R}}$ forwards the same to $SU_{\mathcal {D}}$ and $SU_{\mathcal {T}}$ does EH from PU signal. Residual energy maximization is done under the constraints of energy causality for $SU_{\mathcal {T}}$ and $S_{\mathcal {R}}$ , interference to PU, secondary outage probability and secrecy outage probability. Analytical expressions of ergodic secrecy capacity and secrecy outage probability are derived for non-colluding (NCE) and colluding eavesdropping (CE) scenarios. Closed form expressions for the optimal transmit power of $SU_{\mathcal {T}}$ and $S_{\mathcal {R}}$ along with the time slot for EH are derived and their impacts on the residual energy, secondary outage probability and secrecy outage probability are analysed. Simulation results show a gain on the maximum value of the residual energy by ~8.13% for CE and ~4.72% for NCE over the existing works.